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Abstract
The main focus of this thesis is the modelling, control and stability analysis of
distribution networks with distributed generators and dynamic loads in which the
dynamic loading effects in standard distribution networks are taken into consideration. Different case studies are considered, such as fault effects, a worst-case
scenario and nodal voltage analyses of different network configurations. The dynamic modelling includes line resistance, which has been neglected in the existing
literature, but which the case studies show is a critical parameter affecting system
stability. An LQR controller is proposed for minimising the effect of resistance in
the distribution network. A novel linear zero dynamic controller (LZDC) is design
to maintain the voltage and angle stability for distributed generators. Some elementary notions for the LZDC are introduced such as relative degree, Lie derivative
and exact linearization. This thesis also presents a new concept of a multiple input
multiple output (MIMO) LZDC for a three-phase grid-connected photovoltaic (PV)
system to enhance its stability and robustness under different weather conditions.
Grid-connected PV systems are highly nonlinear systems in which most of the non-
linearities occur due to the intermittency of sunlight and the switching functions of
their converters and inverters. The proposed controller overcomes the limitations of
other controllers, such as the PI, hysteresis, predictive and sliding-mode controllers,
and it is proven that this system operates at unity power factor. The effectiveness of
the proposed control strategies are demonstrated through time-domain simulation
studies conducted using the standard industry-based software environment.