Aspects on Designing Power Electronic Converters for Photovoltaic Application
Viinamäki, Jukka (2017)
Tampere University of Technology
2017
Teknis-taloudellinen tiedekunta - Faculty of Business and Technology Management
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:978-952-15-4072-1
https://urn.fi/URN:ISBN:978-952-15-4072-1
Tiivistelmä
The amount of electrical energy produced by using grid-connected photovoltaic (PV) power plants has increased rapidly during the last decade and the upward trend is expected to continue in the future. The conversion from direct current (dc) produced by the photovoltaic generator (PVG) to alternating current (ac) fed into the grid is made by using the power electronic device called PV inverter. The PV inverter can be implemented using single dc-ac inverter, or there might be an additional voltage boosting dc-dc converter between the PVG and the dc-ac inverter. Corresponding names are single-stage and two-stage PV inverter. Depending on the topology of the dc-ac inverter, it can have single-phase or three-phase grid connection.
When the PV inverter is feeding power to the grid and operating at unity power factor, it is said to operate in grid-feeding mode. In countries, where the share of distributed generation is high, the inverter is also required to operate in grid-supporting mode. In the future, the inverter is possibly required to operate also in grid-forming mode. In this operating mode, the inverter defines the grid voltage and creates the grid locally.
As the amount of installed PV capacity is expected to increase in the future, it becomes increasingly important to design the PV inverters to be reliable, cheap, efficient and able to operate in all the above mentioned operating modes. For this reason, all the topics studied in this thesis are focusing on the design of the PV inverter.
The component sizing and control design of dc-dc converter operating as a part of twostage single-phase PV inverter is studied. The operation in grid-feeding and grid-forming modes are both investigated separately. Also the attenuation of double-line-frequency voltage ripple from the dc-link voltage to the voltage of the PVG, when using dc-link voltage feedforward is studied. The target in the attenuation of the double-line-frequency voltage ripple is to enable using of smaller and more reliable components.
Minimization of the size of the grid filter of single-stage three-phase PV inverter might yield saturating filter inductors. As the trend is towards even more cost-efficient and small inverters, it is important to study the effects of inductor saturation on the performance of the inverter. The simulation model of single-stage grid-connected three-phase photovoltaic inverter having saturating L-filter inductors is developed. The developed model is used for studying the effect of saturating filter inductors on the low-frequency and switching-frequency current harmonics produced by the inverter.
When the PV inverter is feeding power to the grid and operating at unity power factor, it is said to operate in grid-feeding mode. In countries, where the share of distributed generation is high, the inverter is also required to operate in grid-supporting mode. In the future, the inverter is possibly required to operate also in grid-forming mode. In this operating mode, the inverter defines the grid voltage and creates the grid locally.
As the amount of installed PV capacity is expected to increase in the future, it becomes increasingly important to design the PV inverters to be reliable, cheap, efficient and able to operate in all the above mentioned operating modes. For this reason, all the topics studied in this thesis are focusing on the design of the PV inverter.
The component sizing and control design of dc-dc converter operating as a part of twostage single-phase PV inverter is studied. The operation in grid-feeding and grid-forming modes are both investigated separately. Also the attenuation of double-line-frequency voltage ripple from the dc-link voltage to the voltage of the PVG, when using dc-link voltage feedforward is studied. The target in the attenuation of the double-line-frequency voltage ripple is to enable using of smaller and more reliable components.
Minimization of the size of the grid filter of single-stage three-phase PV inverter might yield saturating filter inductors. As the trend is towards even more cost-efficient and small inverters, it is important to study the effects of inductor saturation on the performance of the inverter. The simulation model of single-stage grid-connected three-phase photovoltaic inverter having saturating L-filter inductors is developed. The developed model is used for studying the effect of saturating filter inductors on the low-frequency and switching-frequency current harmonics produced by the inverter.
Kokoelmat
- Väitöskirjat [4864]