 Open Access
 Total Downloads : 16
 Authors : Mrs. A. Sugasini, S. Meenaparameswari, R. Dhanasri, R. Kudiyarasu
 Paper ID : IJERTCONV7IS02056
 Volume & Issue : ICONEEEA – 2k19 (Volume 7 – Issue 02 )
 Published (First Online): 13042019
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
A Novel based Common Mode Current for TransformerLess PV Grid Connected Inverter using H5D Topology
Mrs. A. Sugasini Asst Prof/EEE
S. Meenaparameswari, R. Dhanasri, R. Kudiyarasu
Final Year EEE
Dhanalakshmi Srinivasan Engineering College, Perambalur
Abstract: An improved H5 topology, namely H5D topology, is proposed, in which a clamping diode is added on the basis of H5 topology to eliminate the commonmode voltage fluctuation in H5 topology. Further, the PSIM simulation results of the H5D topology and H5 topology are given and compared, especially; the performance of H5D topology for commonmode current suppression is presented and analyzed concretely. Finally, the experimental prototypes of the H5D topology and H5 topology are built and tested, and the experimental results validate the advantages of the H5D topology. The proposed H5D topology provides a new practical topology for distributed photovoltaic grid connected power generation systems.
INTRODUCTION
Photovoltaic (PV) gridconnected inverters fall into two categories, namely transformer isolation PV inverters and transformer less PV inverters. The transformer less PV inverters have the advantages on small size, low cost and high efficiency compared with the transformer isolation PV inverters. However, the commonmode (CM) currents of the transformer less PV inverters could flow through the parasitic capacitor between the PV array and the ground, which will lead to serious electromagnetic interference and insecurity, and reduce the reliability of the PV inverter systems in practice, such as the hybrid energy storage systems. Therefore, the CM current suppression of transformer less PV inverters has become a hot issue in recent decades.
In order to eliminate or suppress CM current, lots of new topologies have been proposed for the transformer less PV inverters . In these topologies, the CM current is reduced by separating PV array away from the grid or by adding extra clamp circuit to keep CM voltage constant . For the methods of separating PV array away from the grid, some switches are added into the existing topologies, such as H5 topology, in which a switch is added between the input and the bridge arms . In oH5 topology, a switch branch is added between the input and the midpoints of bridge arms on the basis of H5 topology . In H6 family topologies, two switches are added between the input and the bridge arms, or just added into the bridge arms .
In HERIC family topologies, the extra freewheeling branch is added between the bridge arm and
filter inductors. For the methods of adding extra clamp circuit, normally a clamp circuit will be added to clamp the midpoints voltage of the bridge arms, such as, the neutral clamp HERIC topology, in which a clamp circuit is added between the midpoint of input capacitors and freewheeling branch. In HERIC family topologies, the extra freewheeling branch is added between the bridge arm and filter inductors. For the methods of adding extra clamp circuit, normally a clamp circuit will be added to clamp the midpoints voltage of the bridge arms, such as, the neutral clamp HERIC topology, in which a clamp circuit is added between the midpoint of input capacitors and freewheeling branch. Also in HBZVR topology, a clamp circuit containing a switch and five diodes are added between the midpoint of input capacitors and the midpoint of bridge arms based on fullbridge topology.
OBJECTIVES
The objectives of our project are to reduce common mode leakage current and to improve efficiency.
EXISTING SYSTEM
CM current suppression of transformer less PV inverters
CM current suppression of transformer less PV inverters has become a hot issue in recent decades. In order to eliminate or suppress CM current, lots of new topologies have been proposed for the transformer less PV inverters. In these topologies, the CM current is reduced by separating PV array away from the grid or by adding extra clamp circuit Modulation strategies have been proposed to keep the CM voltage constant and reduce the CM current. For example, the bipolar modulation strategy was proposed to keep CM voltage constant for the fullbridge topology with four switches.
Bipolar modulation strategy
Modulation strategies have been proposed to keep the CM voltage constant and reduce the CM current. For example, the bipolar modulation strategy was proposed to keep CM voltage constant for the fullbridge topology with four switches. Unfortunately, in fullbridge topology with the bipolar modulation, high losses and double inductance are unavoidable due to the twolevel bipolar output voltage. Doublefrequency SPWM strategy
The doublefrequency SPWM strategy was proposed to keep CM voltage constant for the threelevel output H6 topology. However, the modulation strategies are proposed for specific topologies, and these topologies are complicated because of the additional devices. Transformerless inverters are increasing popularity in USA after European and Australian markets.
CIRCUIT DIAGRAM
DISADVANTAGES

Insecurity

Large electromagnetic interference process

Reduce reliability process
PROPOSED SYSTEM
To effectively suppress CM current in the inverter with H5 topology, this paper provides an improved H5 topology, namely, H5D topology H5D topology and its modulation strategy for transformer less PV inverters are proposed in this paper, which can effectively suppress the CM currents of the PV inverters. And the proposed H5D topology only includes five switches and a diode. Using the improved modulation strategy, the CM voltage of the inverter with H5D topology can keep constant and the CM current is only about onethird of that with H5 topology in the case that using the same electrical parameters and power switches.
ADVANTAGES

High efficiency

Low cost process

Effective suppression process
The Proposed H5D Topology
To get the constant CM voltage, the H5D topology is proposed, which is composed of five switches ( 1S 5 S ) and a clamping diode c D , as shown in Fig. 4. Where, in1 C ,in2 C and c D constitute the passive clamp circuit, and it is used to clamp the voltages of the bridge midpoints in H5D topology. To introduce the operating principle of the proposed H5D topology, its modulation strategy is also provided.
Figure 3.2 H5D topology circuit diagram
Modulation Strategy of H5D Topology
According to the basic modulation strategy, the unipolar SPWM technique is employed in the proposed H5D topology, which is shown in Fig. 5, where c v is carrier wave and m v is modulation wave. In the positive half period, 1 S and 5 S have the same driving signals, 1 S and 3 S have the opposite driving signals. In the negative half period, 2 S and 5 S have the same driving signals, 2 S and 4 S have the opposite driving signals.
Operating Modes of H5D Topology
According to the operating principle of the proposed H5D topology, there are six operating modes. In the positive half period of grid voltage, there are Mode 1, Mode 2 and Mode 6, and in the negative half period of grid voltage, there are Mode 3, Mode 4 and Mode 5, as shown in Fig. 6.
Mode 1: S1,S4and S5are turned on
Mode 2: S1and S5are turned off, S3and S4are turned on Mode 3: S2, S3 and S5are turned on
Mode 4: S2and S5are turned off, S3 and S4 are turned on Mode 5: After the grid voltage crosses over the zero point
from the positive half period, the current of filter inductors will continuously flow through the antipaallel diodes of S2, S3and S5.
Mode 6: After the grid voltage crosses over the zero point from the negative half period, the current of filter inductors will continuously flow through the antiparallel diodes of S1, S4 and S5.
Inductors will continuously flow through the antiparallel diodes of S1, S4 and S5.
(C)
(a)
(b) (d)
4 The control strategy of H5D Topology
To verify the function of the proposed H5D topology, the control strategy in [42] is adopted in this paper, as seen in Fig. It is a common control strategy for single phase inverter with proportionalresonant (PR) controller, where, the grid connected current, grid iis taken as the control variable, the grid voltage is sampled to obtain its phase and PR controller and SPWM are employed to get the required grid connected current.
Figure 3.5 the control strategy H5 topology
5.6 EXPERIMENTAL RESULTS OF H5D TOPOLOGY
CONCLUSION
A H5D topology and its modulation strategy for transformerless PV inverters are proposed in this paper, which can effectively suppress the CM currents of the PV inverters. And the proposed H5D topology only includes five switches and a diode. Using the improved modulation strategy, the CM voltage of the inverter with H5D topology can keep constant and the CM current is only about onethird of that with H5 topology in the case that using the same electrical parameters and
power switches. The simulation and experimental results validate the effectiveness of the proposed H5D topology and the correctness of the theoretical analysis in this paper. Therefore, H5D topology provides a good choice for single phase transformer less PV inverters due to its simplicity and practicality.
REFERENCES

R. GonzÃ¡lez, J. LÃ³pez, P. Sanchis and L. Marroyo, Transformerless inverter for singlephase photovoltaic systems, IEEE Trans. PowerElectron., vol. 22, no. 2, pp. 693697, Mar. 2007.

R. GonzÃ¡lez, E. GubÃa, J. LÃ³pez and L. Marroyo, Transformerless singlephase multilevelbased photovoltaic inverter, IEEE Trans. Ind.Electron., vol. 55, no. 7, pp. 2694 2702, Jul. 2008.

H. Jedtberg, A. Pigazo, M. Liserre, and G. Buticchi, Analysis of the robustness of transformerless PV inverter topologies to the choice of power devices, IEEE Trans. Power Electron., vol. 32, no.7, pp. 5248 5257, Jul. 2017.

R. R. de Lima, F. C. Melo, L. S. Garcia, E. A. A Coelho, V.
J. Farias and L. C. G. Freitas, Design and modeling of a transformerless hybrid inverter system using a fuel cell as energy storage element for microgrids with sensitive loads, Proc. IEEE 6th Int. Symposium on Power Electron.for Distributed Generation Sys., Aachen, Germany, Jun. 2015, pp. 18.

H. Xiao and S. Xie, Leakage current analytical model and application in singlephase transformerless photovoltaic grid connected inverter, IEEE Trans. Electromagnetic Compatibility, vol. 52, no. 4, pp. 902913, Nov. 2010.

L. S. Garcia, G. M. Buiatti, L. C. de Freitas, E. A. A. Coelho,
V. J. Farias and L. C. Gomes de Freitas, Dual transformerless singlestage current source inverter with energy management control strategy, IEEE Trans.Power Electron., vol. 28, no. 10, pp. 46444656, Oct. 2013.

V. Sonti, S. Jain and S. Bhattacharya, Analysis of the modulation strategy for the minimization of the leakage current in the PV gridconnected cascaded multilevel inverter, IEEE Trans. Power Electron., vol. 32, no. 2, pp. 11561169, Feb. 2017.

W. Li, Y. Gu, H. Luo, W. Cui, X. He and C. Xia, Topology review and derivation methodology of singlephase transformerless photovoltaic inverters for leakage current suppression, IEEE Trans. Ind. Electron., vol. 62, no. 7, pp. 45374551, Jul. 2015.

S. A. Khan, Y. Guo and J. Zhu, A high efficiency transformerless PV gridconnected inverter with leakage current suppression, Proc. 20169th Int. Conf. on Electric. and Computer Eng., Dhaka, Bangladesh, Dec. 2016, pp. 190 193.

M. Victor, F. Greizer, S. Bremicker, and U. Hubler, Method of converting a direct current voltage from a source of direct current voltage, more specially from a photovoltaic source of direct current voltage, into alternating current voltage, U.S. Patent 7 411 802 B2, Jun. 2005.

H. Xiao, S. Xie, Y. Chen and R. Huang, An optimized transformerless photovoltaic gridconnected inverter, IEEE Trans. Ind. Electron., vol. 58, no. 5, pp. 18871895, May 2011.

L. Zhang, K. Sun, Y. Xing and M. Xing, H6 transformerless fullbridge PV gridtied inverters, IEEE Trans. Power Electron., vol. 29, no. 3, pp. 12291238, Mar. 2014.

B. Ji, J. Wang and J. Zhao, Highefficiency singlephase transformerless PV H6 inverter with hybrid modulation method, IEEE Trans. Ind.Electron., vol. 60, no. 5, pp. 2104 2115, May 2013.

W. Yu, J. S. J. Lai, H. Qian and C. Hutchens, High efficiency MOSFET inverter with H6type configuration for photovoltaic non isolated ACmodule applications, IEEE Trans. Power Electron., vol. 26, no. 4, pp. 12531260, Apr. 2011.

M. Islam and S. Mekhilef, H6type transformerless single phase inverter for gridtied photovoltaic system, IET Power Electron., vol. 8, no. 4, pp. 636644, Apr. 2015.

W. Cui, B. Yang, Y. Zhao, W. Li and X. He, A novel singlephase transformerless gridconnected inverter, Proc. 37th Annu. Conf. IEEEInd. Electron. Soc., Melbourne, VIC, Nov. 2011, pp. 11261130.

H. Schmidt, C. Siedle, and J. Ketterer, DC/AC converter to convert direct electric voltage in alternating voltage or into alternating current, Patent 7 046 534 B2, Feb. 2004.

S. Hu, C. Li, W. Li, X. He and F. Cao, Enhanced HERIC based transformerless inverter with hybrid clamping cell for leakage current elimination, Proc. IEEE Energy Convers. Cong. and Expo., Montreal, QC, Sept. 2015, pp. 53375341.