TY - JOUR
T1 - Coupled-Inductor-Based DC Current Measurement Technique for Transformerless Grid-Tied Inverters
AU - Abdelhakim, Ahmed
AU - Mattavelli, Paolo
AU - Yang, Dongsheng
AU - Blaabjerg, Frede
PY - 2018/1
Y1 - 2018/1
N2 - Grid-tied photovoltaic inverters must fulfill several requirements, including high efficiency and reduced cost and complexity of the overall system. Hence, transformerless operation is advantageous in order to achieve the prior requirements. Meanwhile, such operation results in several demerits, such as the dc current component injection into the grid. This component should be effectively mitigated in order to avoid some impacts, such as the saturation of the transformers in the distribution network. On the other hand, limiting this component up to few milliamperes is a challenging issue due to the various measurement errors. Accordingly, different blocking and measurement techniques have been proposed and studied to overcome this issue, where some demerits are seen behind each technique such as the implementation complexity, the common-mode voltage problems, and the high filter requirements. Moreover, none of them measures the dc component directly, but predicts its value using different approaches. Hence, this letter proposes a new technique to measure this dc current component with high accuracy using a coupled inductor combined with a small-range Hall effect current sensor in order to achieve the lowest possible cost with the highest possible accuracy. The proposed technique is introduced, analyzed, and tested experimentally to verify its principle of operation. Also experimental measurement of the dc current component using a 5-kVA transformerless grid-tied voltage-source inverter is introduced with and without the proposed technique in order to validate its operation.
AB - Grid-tied photovoltaic inverters must fulfill several requirements, including high efficiency and reduced cost and complexity of the overall system. Hence, transformerless operation is advantageous in order to achieve the prior requirements. Meanwhile, such operation results in several demerits, such as the dc current component injection into the grid. This component should be effectively mitigated in order to avoid some impacts, such as the saturation of the transformers in the distribution network. On the other hand, limiting this component up to few milliamperes is a challenging issue due to the various measurement errors. Accordingly, different blocking and measurement techniques have been proposed and studied to overcome this issue, where some demerits are seen behind each technique such as the implementation complexity, the common-mode voltage problems, and the high filter requirements. Moreover, none of them measures the dc component directly, but predicts its value using different approaches. Hence, this letter proposes a new technique to measure this dc current component with high accuracy using a coupled inductor combined with a small-range Hall effect current sensor in order to achieve the lowest possible cost with the highest possible accuracy. The proposed technique is introduced, analyzed, and tested experimentally to verify its principle of operation. Also experimental measurement of the dc current component using a 5-kVA transformerless grid-tied voltage-source inverter is introduced with and without the proposed technique in order to validate its operation.
KW - Coupled inductor
KW - Current sensor
KW - Current transformer
KW - DC current
KW - Grid-tied inverters
KW - Photovoltaic
KW - Renewable energy sources
KW - Transformerless
KW - Voltage-source inverter (VSI)
UR - http://www.scopus.com/inward/record.url?scp=85032176315&partnerID=8YFLogxK
U2 - 10.1109/TPEL.2017.2712197
DO - 10.1109/TPEL.2017.2712197
M3 - Journal article
SN - 0885-8993
VL - 33
SP - 18
EP - 23
JO - I E E E Transactions on Power Electronics
JF - I E E E Transactions on Power Electronics
IS - 1
M1 - 7938667
ER -