Document Text Contents
Page 1
by Ying LIU
April 2009
Thesis submitted to the Department of Engineering,
University of Leicester for the degree of Doctor of Philosophy
Page 2
DEPARTMENT OF ENGINEERING
ADVANCED CONTROL
OF PHOTOVOLTAIC CONVERTERS
by
Ying LIU
Thesis submitted to the Department of Engineering, University of Leicester for
the degree of Doctor of Philosophy
April 2009
Page 88
82
or closing the switch.
Fig 5-2 demonstrates the P (I) characteristics of a Thevenin source (a) and a real PV
source (b). It can be seen that they both exhibit a maximum power point (MPP) within
their operating range. Changing RS has a similar effect as the change of irradiance E on
the P (I) characteristics. Therefore, a Thevenin source with switchable series resistance
can be used to study and test certain Maximum Power Point Tracking (MPPT) algorithms
such as hill climbing methods.
However, there are a number of limitations to this approach. Firstly, a Thevenin source is
a good approximation only around the MPP. Also, having only changes in RS does not
reflect the actual characteristics of a PV source. For a real PV source, VS changes
together with RS, under the effect of irradiance and temperature. Therefore, a Thevenin
source can not be used for more complicated or more specific study purposes.
Furthermore, the scope of the present study includes the effect of PV dynamics due to PV
cell capacitance on MPPT algorithms (see Chapter 3). It also includes the detection of
occurrence of partial shading and the development of methods to control the converters to
work at the global maximum power point under partial shading conditions (see Chapter
4). The existing PV source emulator in the form of a simple Thevenin source is unable to
emulate such situations. Therefore, a more practical PV source emulator is needed to
verify the true performance of MPPT algorithms and other aspects of intelligent control.
One possible implementation of a PV source emulator is the use of multiple DC power
supplies with a feedback circuit and fast switches so that the output voltage-current
curves follow a typical PV source characteristic. The fast switches are needed because
Page 89
83
power supplies usually have a large capacitance at the output, which means that the
output voltage can not change quickly. However, with such an emulator it would be
difficult to emulate partial shading conditions which cause multiple local maxima in the
PV characteristic.
(a) Thevenin Source
(b) Real PV source
Fig 5-2. P-I characteristics
Page 176
[70] Reactive sputtering produces durable coatings for a demanding environmental test
application, http://www.ptbmagazine.com/Jan00/ptb.0100coat.html, accessed
30/09/2008
[71] John G. Webster, Wiley Encyclopedia of Electrical and Electronics Engineering,
John Wiley, 1999, ISBN: 0471139467
[72] Glenn James, Mathematics dictionary, Van Nostrand Reinhold, 1976, ISBN:
0442240910
[73] J. E. Kaufman and J. F. Christensen, IES Lighting Handbook, Illuminating
Engineering Society of North America, 5th edition 1972, ISBN: 0879950005
[74] Juno and Aculux Residential Recessed Lighting, http://www.junolightinggroup.com/,
accessed 02/07/2009
[75] Binning and Labelling, http://www.philipslumileds.com/pdfs/AB21.pdf, accessed
30/09/2008
[76] Luxeon K2 Emitter, http://www.philipslumileds.com/pdfs/DS51.pdf, accessed
30/09/2008
[77] All in One Plug and Play Guide, http://www.philipslumileds.com/pdfs/PG01.pdf,
accessed 30/09/2008
[78] Wide Area Lighting Design Guide, http://www.philipslumileds.com/pdfs/BR07.pdf,
accessed 30/09/2008
[79] Mega-Ray SB 100-Watt flood lamp, www.reptielenlampen.nl/MegaRay.htm,
accessed 30/09/2008
[80] C. Prapanavarat, M. Barnes and N. Jenkins, “Investigation of the performance of a
photovoltaic AC module”, IEE Proceedings: Generation, Transmission and
Distribution, Vol. 149, Issue 4, pp. 472-478
[81] www.osram.com, accessed 30/09/2008
[82] DIALux - a planning software for your project presentation,
http://www.dial.de/CMS/English/Articles/DIALux/Features/Features.html, accessed
30/09/2008
[83] http://www.mirosolar.com/reflection.html, accessed 30/09/2008
[84] TMS320F281x Data Sheet, http://focus.ti.com/lit/ds/symlink/tms320f2812.pdf,
accessed 30/09/2008
Page 177
Publications
[1] Y. Liu, and J.A.M. Bleijs, “Dynamic Effect of PV Cell Capacitance on MPPT
Algorithms”, Proceedings of the 21st European Union Photovoltaic Solar Energy
Conference, Dresden, 4-8 September 2006, pp. 2604- 2607
[2] Y. Liu, and J.A.M. Bleijs, “Design of a Flexible Solar Emulator to Facilitate the
Study on MPPT Control of PV Panels Using a DSP Based DC/DC Converter”,
Proceedings of the 22nd European PV Solar Energy Conference, 3 - 7 September
2007, Milan, pp. 3059-3063
by Ying LIU
April 2009
Thesis submitted to the Department of Engineering,
University of Leicester for the degree of Doctor of Philosophy
Page 2
DEPARTMENT OF ENGINEERING
ADVANCED CONTROL
OF PHOTOVOLTAIC CONVERTERS
by
Ying LIU
Thesis submitted to the Department of Engineering, University of Leicester for
the degree of Doctor of Philosophy
April 2009
Page 88
82
or closing the switch.
Fig 5-2 demonstrates the P (I) characteristics of a Thevenin source (a) and a real PV
source (b). It can be seen that they both exhibit a maximum power point (MPP) within
their operating range. Changing RS has a similar effect as the change of irradiance E on
the P (I) characteristics. Therefore, a Thevenin source with switchable series resistance
can be used to study and test certain Maximum Power Point Tracking (MPPT) algorithms
such as hill climbing methods.
However, there are a number of limitations to this approach. Firstly, a Thevenin source is
a good approximation only around the MPP. Also, having only changes in RS does not
reflect the actual characteristics of a PV source. For a real PV source, VS changes
together with RS, under the effect of irradiance and temperature. Therefore, a Thevenin
source can not be used for more complicated or more specific study purposes.
Furthermore, the scope of the present study includes the effect of PV dynamics due to PV
cell capacitance on MPPT algorithms (see Chapter 3). It also includes the detection of
occurrence of partial shading and the development of methods to control the converters to
work at the global maximum power point under partial shading conditions (see Chapter
4). The existing PV source emulator in the form of a simple Thevenin source is unable to
emulate such situations. Therefore, a more practical PV source emulator is needed to
verify the true performance of MPPT algorithms and other aspects of intelligent control.
One possible implementation of a PV source emulator is the use of multiple DC power
supplies with a feedback circuit and fast switches so that the output voltage-current
curves follow a typical PV source characteristic. The fast switches are needed because
Page 89
83
power supplies usually have a large capacitance at the output, which means that the
output voltage can not change quickly. However, with such an emulator it would be
difficult to emulate partial shading conditions which cause multiple local maxima in the
PV characteristic.
(a) Thevenin Source
(b) Real PV source
Fig 5-2. P-I characteristics
Page 176
[70] Reactive sputtering produces durable coatings for a demanding environmental test
application, http://www.ptbmagazine.com/Jan00/ptb.0100coat.html, accessed
30/09/2008
[71] John G. Webster, Wiley Encyclopedia of Electrical and Electronics Engineering,
John Wiley, 1999, ISBN: 0471139467
[72] Glenn James, Mathematics dictionary, Van Nostrand Reinhold, 1976, ISBN:
0442240910
[73] J. E. Kaufman and J. F. Christensen, IES Lighting Handbook, Illuminating
Engineering Society of North America, 5th edition 1972, ISBN: 0879950005
[74] Juno and Aculux Residential Recessed Lighting, http://www.junolightinggroup.com/,
accessed 02/07/2009
[75] Binning and Labelling, http://www.philipslumileds.com/pdfs/AB21.pdf, accessed
30/09/2008
[76] Luxeon K2 Emitter, http://www.philipslumileds.com/pdfs/DS51.pdf, accessed
30/09/2008
[77] All in One Plug and Play Guide, http://www.philipslumileds.com/pdfs/PG01.pdf,
accessed 30/09/2008
[78] Wide Area Lighting Design Guide, http://www.philipslumileds.com/pdfs/BR07.pdf,
accessed 30/09/2008
[79] Mega-Ray SB 100-Watt flood lamp, www.reptielenlampen.nl/MegaRay.htm,
accessed 30/09/2008
[80] C. Prapanavarat, M. Barnes and N. Jenkins, “Investigation of the performance of a
photovoltaic AC module”, IEE Proceedings: Generation, Transmission and
Distribution, Vol. 149, Issue 4, pp. 472-478
[81] www.osram.com, accessed 30/09/2008
[82] DIALux - a planning software for your project presentation,
http://www.dial.de/CMS/English/Articles/DIALux/Features/Features.html, accessed
30/09/2008
[83] http://www.mirosolar.com/reflection.html, accessed 30/09/2008
[84] TMS320F281x Data Sheet, http://focus.ti.com/lit/ds/symlink/tms320f2812.pdf,
accessed 30/09/2008
Page 177
Publications
[1] Y. Liu, and J.A.M. Bleijs, “Dynamic Effect of PV Cell Capacitance on MPPT
Algorithms”, Proceedings of the 21st European Union Photovoltaic Solar Energy
Conference, Dresden, 4-8 September 2006, pp. 2604- 2607
[2] Y. Liu, and J.A.M. Bleijs, “Design of a Flexible Solar Emulator to Facilitate the
Study on MPPT Control of PV Panels Using a DSP Based DC/DC Converter”,
Proceedings of the 22nd European PV Solar Energy Conference, 3 - 7 September
2007, Milan, pp. 3059-3063
