efficient single phase transformerless inverter for grid tied pvg system with reactive power control

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Efficient Single Phase Transformer less

Inverter for Grid-Tied PVG System with

Reactive Power Control

Introduction: In general, PV power generation system includes solar arrays and

power conversion unit. In most countries and areas, a line-frequency

transformer or a high-frequency transformer has been utilized in the

grid-tied PV system to create a galvanic isolation between the PV

module and the grid. However, the use of line-frequency or high-

frequency transformer makes the entire system bulky, costly, and less

efficient. In contrast, transformer less PV inverter system has been

drawing more attention for its low cost, high efficiency, small size and

light weight. The exclusion of transformer, and hence its isolation

capability, has to be considered carefully due to the issues raised from

no galvanic isolation between the PV module and the grid. In this case,

because of the parasitic capacitance between the PV module and the

ground, the fluctuating CM voltage that depends on the topology

structure and switching scheme can cause of a capacitive leakage

current. The existence of leakage current increases grid current

harmonics and system losses, deteriorates the electromagnetic

compatibility and, more significantly, lead to a safety threat.

Existing system: Dual-parallel- buck converter, consists of four Cool MOS switches

and four SiC diodes. The main drawback of this topology is that the grid

will be short circuit if no dead time is present between the switches S3

and S4, through which the grid is directly connected. The main



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advantage of these two topologies is that when a phase difference will be

occurred between the output voltage and current, the diodes D1 & D2 or

D3 & D4 will be activated depending on the positive or negative half

cycle. As a result, these topologies may be implemented with MOSFET

switches even when inject reactive power.

Drawbacks:

The grid will be short circuit if no dead time is present between the

switches S3 and S4, through which the grid is directly connected.

Proposed system: The proposed transformer less inverter topology consists of six

MOSFET switches (S1-S6) and six diodes (D1-D6). L1A, L1B, L2A,

L2B, L1g, L2g and Co make up the LCL type filter connected to the

grid. VPV and Cdc represent the input dc voltage and dc link capacitor.

The proposed topology is derived overcome the low reverse-recovery

issues of MOSFETs body-diode when injects reactive power into the

utility grid. Therefore, the proposed topology can be implemented with

MOSFET switches without reliability and efficiency penalty. The



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proposed topology can also employ unipolar-SPWM with three-level

output voltage.

Advantages:

Utilizing MOSFET switches even though when inject reactive

power into the utility grid.

Low leakage current flows through the system

PWM dead time is not required for the proposed topology that

reduces the THD at the output.

Applications: Grid-tied PV system.



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Call: 0413-4205444, +91 9566355386, 99625 88976.



Block diagram:

Solar supply Transformer less

inverter

Load Coupled inductor

Micro-controller circuit

Buffer circuit

Driver circuit

5V DC

Supply

12V

DC

efficient single phase transformerless inverter for grid tied pvg system with reactive power control

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