Small-signal modelling of maximum power point tracking for photovoltaic systems
File(s)
Author(s)
Sokolov, Michael
Type
Thesis
Abstract
In grid connected photovoltaic (PV) generation systems, inverters are used to convert
the generated DC voltage to an AC voltage. An additional dc-dc converter is usually
connected between the PV source and the inverter for Maximum Power Point Tracking
(MPPT). An iterative MPPT algorithm searches for the optimum operating point of PV cells
to maximise the output power under various atmospheric conditions. It is desirable to be able
to represent the dynamics of the changing PV power yield within stability studies of the AC
network. Unfortunately MPPT algorithms tend to be nonlinear and/or time-varying and
cannot be easily combined with linear models of other system elements.
In this work a new MPPT technique is developed in order to enable linear analysis of
the PV system over reasonable time scales. The new MPPT method is based on interpolation
and an emulated-load control technique. Numerical analysis and simulations are employed to
develop and refine the MPPT. The small-signal modelling of the MPPT technique exploits
the fact that the emulated-load control technique can be linearised and that short periods of
interpolation can be neglected. A small-signal PV system model for variable irradiation
conditions was developed. The PV system includes a PV module, a dc-dc boost converter, the
proposed controller and a variety of possible loads. The new model was verified by
component-level time-domain simulations.
Be
cause measured signals
in PV systems contain noise, it is important to assess the
impact of that noise on the MPPT and design an algorithm that operates effectively in
pr
esence of noise. For performance assessment of the new MPPT techniques, the efficiencies
of
various MPPT techniques
in presence of noise were compared. This comparison showed
superiority of the interpolation MPPT and led to conclusions about effective use of existing
MPPT methods.
The new MPPT method was also experimentally tested.
the generated DC voltage to an AC voltage. An additional dc-dc converter is usually
connected between the PV source and the inverter for Maximum Power Point Tracking
(MPPT). An iterative MPPT algorithm searches for the optimum operating point of PV cells
to maximise the output power under various atmospheric conditions. It is desirable to be able
to represent the dynamics of the changing PV power yield within stability studies of the AC
network. Unfortunately MPPT algorithms tend to be nonlinear and/or time-varying and
cannot be easily combined with linear models of other system elements.
In this work a new MPPT technique is developed in order to enable linear analysis of
the PV system over reasonable time scales. The new MPPT method is based on interpolation
and an emulated-load control technique. Numerical analysis and simulations are employed to
develop and refine the MPPT. The small-signal modelling of the MPPT technique exploits
the fact that the emulated-load control technique can be linearised and that short periods of
interpolation can be neglected. A small-signal PV system model for variable irradiation
conditions was developed. The PV system includes a PV module, a dc-dc boost converter, the
proposed controller and a variety of possible loads. The new model was verified by
component-level time-domain simulations.
Be
cause measured signals
in PV systems contain noise, it is important to assess the
impact of that noise on the MPPT and design an algorithm that operates effectively in
pr
esence of noise. For performance assessment of the new MPPT techniques, the efficiencies
of
various MPPT techniques
in presence of noise were compared. This comparison showed
superiority of the interpolation MPPT and led to conclusions about effective use of existing
MPPT methods.
The new MPPT method was also experimentally tested.
Version
Open Access
Date Issued
2013-01
Date Awarded
2013-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Mitcheson, Paul
Green, Tim
Sponsor
Imperial College London
B'nai B'rith
Publisher Department
Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)