Modelling power systems in a long-term power shortage
View/ Open
Date
28/11/2019Author
Heggie, Alastair
Metadata
Abstract
This thesis proposes and analyses decision support models for power systems operating in
chronic power shortage conditions. Mostly these power systems exist in Sub-Saharan Africa,
but other countries, for example Pakistan, Nepal, Cambodia and Bangladesh, suffer from similar
problems. The thesis is structured in three parts looking at demand forecasting, distribution
level load shedding and national level power rationing.
First, we develop methods to forecast the electrical load on a power system conditional on a
policy of load shedding. Our methods are based on the Linear Gaussian State Space Model
and the Kalman Filter. Conventional time series forecasting methods cannot be applied in a
power system operating in a state of chronic load shedding because the observed demand is
determined both by the latent unsuppressed demand and by the load shedding decisions of
the Distribution System Operator. We demonstrate the accuracy of these forecasting methods
on a dataset from a Nigerian electricity distribution company. In addition, these models have
potential to improve estimates of the latent demand for electricity compared to existing methods
that rely on unreliable proxy variables or ’bottom-up’ calculations that are difficult to verify.
Next, we formulate an optimization problem to help Distribution System Operators incorporate
probabilistic demand forecasts such as those developed in this thesis into their planning of
load shedding. Our problem is closely related to a stochastic variant of the classic "knapsack
problem" with random item "weights". We extend the literature on this problem to study the
case where the item weights are given by a stochastic process which is only observed after
an item is included in the knapsack. Our computational experiments provide evidence that the
theoretical benefits of planning ahead are not realized in practice. It seems that for realistic
range of stochastic demand processes a robust policy can be derived by an approach that only
considers immediate costs and benefits.
Finally, we study the problem of balancing supply and demand at the national level.We develop
an AC Optimal Power Flow model with endogenous load shedding and use this to quantify the
trade-off between maximizing the total amount of power delivered and distributing the available
power between regional distribution companies in a fairer way. Our model represents the
situation in the Nigerian power system in which the system operator minimizes load shedding,
subject to exogenous proportional power supply targets for different regions. We explore how
the level of permitted deviation from the target and the time period over which this target is to
be achieved affects the level of load shedding. The use of an AC power flow model complicates
the problem but is necessary because voltage constraints are often binding in highly stressed
transmission networks in countries like Nigeria.
Collections
Related items
Showing items related by title, author, creator and subject.
-
First year interim report on Edinburgh Wave Power Project : Study of mechanisms for extracting power from sea waves
Salter, Stephen Hugh; Jeffrey, David Crighton; Taylor, Jamie Richard Mackenzie (University of EdinburghThe University of Edinburgh, 1975-09)The final decision about the feasibility of wave power needs information about duck performance on the heaving surging rig and on a free floating backbone. On the basis of one year's work I can say that the possibility of ... -
Fourth year report on Edinburgh Wave Power Project : Study on mechanisms for extracting power from sea waves (Volume 1)
Jeffrey, David Crighton; Keller, Glenn Jay; Mollison, Denis; Richmond, D.J.E.; Salter, Stephen Hugh; Taylor, Jamie Richard Mackenzie; Young, Ian A. (The University of Edinburgh, 1978-07) -
Enhancement of Power System Stability Using Fuzzy Logic Based Supervisory Power System Stabilizer
Behbehani, Hussain M. (The University of Edinburgh, 2008)