An Overview of Different Types of 1-Phase Transformerless

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An Overview of Different Types of 1-Phase Transformerless

Transcript Of An Overview of Different Types of 1-Phase Transformerless

May 2016, Volume 3, Issue 5

JETIR (ISSN-2349-5162)

An Overview of Different Types of 1-Phase Transformerless Inverter Topology
1Digesh D. Shah, 2Archana S. Nanoty, 3Amarpal kanogiya Department of Electrical Engineering
Dr. Jivraj Mehta Institute of Technology, Anand, Gujarat

Abstract— Transformerless inverters are widely used in grid-tied Photovoltaic (PV) generation systems, due to the benefits of achieving high efficiency and low cost. Various transformerless inverter topologies have been proposed to meet the safety requirement of leakage currents, such as specified in the VDE 4105 standard. In this paper, a family of H5 transformerless inverter topologies with low leakage currents is proposed highly efficient and reliable inverter concept (HERIC) topology has been discussed with Matlab simulation [1].

the inverter output voltage is at zero Voltage level, and the leakage current path is cut off.[1] Shown in Fig.1

Index Terms—Common-mode voltage, grid-tied inverter, leakage Current, photovoltaic (PV) generation system, transformerless inverter.
I. INTRODUCTION THE applications of distributed photovoltaic (PV) generation systems in both commercial and residential structures have rapidly increased during recent years. Although the price of PV panel has been declined largely, the overall cost of both the investment and generation of PV grid-tied system are still too high, comparing with other renewable energy sources. Therefore, the grid-tied inverters need to be carefully designed for achieving the purposes of high efficiency, low cost, small size, and low weight, especially in the low-power single-phase systems (less than 5 kW). From the safety point of view, most of the PV grid-tied inverters employ line-frequency transformers to provide galvanic isolation in commercial structures in the past. However, line-frequency transformers are large and heavy, making the whole system bulky and hard to install. Compared with line-frequency isolation, inverters with high-frequency isolation transformers have lower cost, smaller size and weight. However, the inverters with highfrequency transformers have several power stages, which increase the system complexity and reduce the system efficiency [1]–[6]. As a result, the transformerless PV gridtied inverters are widely Installed in the low-power distributed PV generation systems. Unfortunately, when the transformer is removed, the common mode (CM) leakage currents (leakage) may appear in the system and flow through the parasitic capacitances between the PV panels and the ground [7], [8]. Moreover, the leakage currents lead to serious safety and radiated interference issues [9]. Therefore, they must be limited within a reasonable range [10].

Fig.1. H5 Topology (1) 2. HERIC Topology
The HERIC topology shown in Fig. 2 employs two extra switches on the ac side of inverter, so the leakage current path is cut off as well.[1]
Fig.2. HERIC Topology (2)
III. CONDUCTION MODE OF INVERTER TOPOLOGY  Conduction Mode of H5 Topology
There are four operation modes. Fig.3 shows that, in mode (1), S5, S1, S4 Switches conduct. In Mode (2) S1 & freewheeling diode conduct for dissipating energy.Same as in Mode (3) S5, S2, S3 Switches conduct. And In Mode (4) S3 & Freewheeling diode conduct.

II. PRAPOSED INVERTER TOPOLOGIES

1. H5 Topology

It employs an extra switch on the dc side of inverter. As a result, the PV array is disconnected from the utility grid when

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Fig.4. Conduction Modes of HERIC Topology

Fig. 3. Conduction Modes of H5 Topology
 Conduction Mode of HERIC Topology
There are four operation modes. Fig.4 Shows that, In mode (1) S1, S4 Switches conduct. In Mode (2) S5, S6 Switches conduct. Same as in Mode (3) S2, S3 Switches conduct.. And In Mode (4) S5, S6 Switches conduct.

IV. TRIGGERING TECHNIQUE FOR INVERTER TOPOLOGIES
 SPWM Technique
The gating signal generated by sinusoidal reference signal with triangular carrier wave of frequency fc. This sinusoidal modulation is commonly used in industrial application. The frequency of reference fr signal is determine the inverter output frequency fo and its peak amplitude Ar controls the modulation index M and turns the RMS output voltage Vo. comparing the bidirectional carrier signal Vcr with two sinusoidal reference signal vr and –vr . [11],[12] The output voltage is Vo= V1 (g1- g4)

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May 2016, Volume 3, Issue 5

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SPWM TECH.

1 0 -1
0 1.5
1 0.5
0 0

0.01 0.01

0.02 0.02

0.03 0.03

0.04 0.04

0.05 0.05

0.06 0.06

1 0 -1
0 1.5
1 0.5
0 0

0.01 0.01

0.02 0.02

0.03 0.03 Time

0.04 0.04

0.05 0.05

0.06 0.06

Fig.5. Simulation of SPWM Technique [11]-[12]

V. SIMULATION OF INVERTER TOPOLOGIES WITH MATLAB
A. Simulation and Output Result of HERIC Topology with SPWM Technique

Load Current (A)

100

50

0

-50

-100

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Time (S)

300

200

100

0

-100

-200

-300

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Time (S)

Fig. 7. Simulation & O/P Result of H5 Topology

Load Voltage (V)

Fig.7. shows that simulation and output results of H5 Topology

Load Current (A)

60 40 20
0 -20 -40 -60
0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Time (s)

200 100
0 -100 -200
0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

Time (S)

Fig.6. Simulation O/P Result of HERIC Topology

Load Voltage (V)

Fig.6. shows that simulation and output results of HERIC Topology

B. Simulation and Output Result of H5 Topology with SPWM Technique

VI. CONCLUSION

A novel single-phase transformerless grid-connected PV Inverter, which generates no ground leakage current, is proposed in this paper. The efficiency of the proposed Inverter is high. Finally, the simulated results both verify the theoretical analysis.

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