Transformerless Single-Phase Grid-Connected PV System.

1. IIT(ISM) DHANBAD
Presented By:
PRAVEEN KUMAR
Roll: 15MT000094
M.TECH(PEED)
DEPARTMENT OF ELECTRICAL ENGINEERING
Dissertation Report Presented
On

2.  Introduction of PV system
 Basics of PV cell : Construction and Mathematical Modelling
 PV cell Usage
 Block Diagram and Simulation Diagram of Integration of PV energy sources into the
electrical grid
 H6 Inverter Topology
 Simulation Results
 Discussion and Conclusion
 Future work and Future Scope
 References

3.  In the present global energy and environmental context, the aim of
reducing the emissions of greenhouse gases and polluting substances
 Increasing number of renewable energy sources and distributed
generators.
 New strategies for the operation and management of the electricity
grid.
 Improve the power-supply reliability and quality.
 Liberalization of the grids leads to new management structures
 Grid-Connected photovoltaic (PV) systems, particularly low-power
single-phase systems (up to 5 kW), are becoming more important
worldwide.

4.  PV systems as an alternative energy resource
 Complementary Energy-resource in hybrid systems
 Fast evolution, due to:
a. development of fast semiconductor switches
b. introduction of real-time controllers
Necessary:
• high reliability
• high efficiency
• reasonable cost
• smaller size & weight

5.  PV cell generates a voltage around 0.5 to 0.8 volts depending on the
semiconductor and the built up technology
 To get the required voltage ,tens of PV cells are connected in series to
form a PV Module followed by interconnection in series and/or parallel
to form a PV Panel as shown
PV Cells PV Module PV Panel PV Array

6.  Three major families of PV cells :
1. Mono Crystalline Technology:
• more efficient and more expensive
• efficiency is in between 10% to 15%
2. Poly Crystalline Technology:
• most commonly used in photovoltaic and less expensive
• efficiency is in between 9% to 12%
3. Thin film Technology:
• reduces the amount of active material in a cell
• panels are approximately twice as heavy as crystalline silicon panels
• efficiency is 10% for a Si, 9% for CdTe(Cadmium telluride) etc

7.  An equivalent circuit of a practical PV cell of two diode model
Current to the load:
𝑰 = 𝑰𝒑𝒉 − 𝑰𝒔𝟏 𝒆𝒙𝒑
𝑽+𝑰𝑹𝒔
𝒏𝟏𝑽𝒕
− 𝟏 − 𝑰𝒔𝟐 𝒆𝒙𝒑
𝑽+𝑰𝑹𝒔
𝒏𝟐𝑽𝒕
− 𝟏 −
𝑽+𝑰𝑹𝒔
𝑹𝒑
Where,
Iph is the photocurrent
Is1 , Is2 reverse saturation current of corresponding diodes
K is Boltzmann constant (K= 1.38× 10-23 m2 kg s-2 K-1)
Vt is Thermal voltage equivalent
n1 and n2 are ideality factor of diode
Rs & Rp are the series and shunt resistors of the cell

8.  wide range of input voltage and input power
 very wide ranges as functions of solar irradiation and ambient temperature
 Output of PV cell :
I -V graph for PV cell is as: (Y-axis as “I”& X-axis as “V”) P-V graph for PV cell is as: (Y-axis as “P” & X-axis as “V”)

9.  PV is widely used as an alternative energy sources which are used as
 PV cells - connected to the grid (Grid-tied System)
 PV cells - isolated power supplies (Standalone System)
 Isolation is acquired using a transformer that can be placed on either the
grid or low frequency (LF) side or on the HF side

10.  Transformerless PV Grid-tied System
PV Array H6
Inverter
Topology
Distribution
Panel
AC Loads
Utility Grid
AC
Filters

11.  Transformerless single phase photovoltaic inverter has attracted power
generation system due to its
 higher efficiency and low cost
 Small size and low weight
 Limitations
 On removing the transformer the common mode leakage current appear & flow
through the parasitic capacitances between the PV panel and Ground.
Fig: Leakage current path for transformerless PV inverters
 The leakage current has to be controlled to avoid EMI problem, circuit
damage and safety issues.

12.  The output of PV cell is connected to the inverter from which three level signal
is obtained i.e. it operates in
 Active mode in the Positive half Period
 Freewheeling mode in the Positive half Period
 Active mode in the Negative half Period
 Freewheeling mode in the Negative half Period
 Main job of H6 topology is to eliminate leakage currents, by keeping the CM voltage
constant for making it more efficient & have minimum loss
 The modified H-bridge topology is significantly advantageous over other topologies,
i.e., less power switch, power diodes, high power quality waveforms, low switching
losses, and high-voltage capability.
 The proposed single-phase H6 inverter was developed from the H5 inverter topology. It
comprises a single-phase conventional H-bridge inverter.

13. Switches
Modes
S1 S2 S3 S4 S5 S6
Positive Half
Period ON OFF OFF ON ON OFF
Freewheeling
in positive half
period
ON OFF OFF OFF OFF OFF
Negative Half
Period OFF ON ON OFF OFF ON
Freewheeling
in negative half
period
OFF OFF ON OFF OFF OFF
 The CM voltage of the proposed topology in each operation mode is equals to 0.5U PV, and it
results in low leakage current characteristic of the proposed H6 topologies with VAB = U PV .

15.  Grid output voltage waveform
 Grid output current waveform

16.  Phase voltage of H6 Inverter(VAN)
Phase voltage of H6 Inverter(VBN)

17.  Output Line Voltage of H6 Inverter(VAB)
Leakage current waveform in Amperes

18.  This presented a single phase H6 Transformerless Full-Bridge PV
(Photovoltaic) Grid-Tied system which is highly efficient , having
low cost and smaller in size & weight.
 The circuit topology, control circuits and operational principal of
the proposed inverter were analysed in details.
 The main goal of the proposed work is to control the leakage
current by keeping the common mode voltage constant.

19.  Power-electronic technology plays a very important role in the field of
renewable energy sources
 Optimize the energy conversion and transmission
 Minimize harmonic distortion and leakage current
 To achieve at a low cost a high efficiency over a wide power range
 Achieve a high reliability
 The trend of the PV energy leads to consider that it will be an interesting
alternative in the near future

20.  DC-current injection is of great interest in transformerless PV
inverters
 Improving the Inverter controlling circuit
 Multilevel Inverters can be used by controlling the Flying capacitor
voltage method

21.  very efficient PV cells
 roofing PV systems
 PV modules in high building structures

22.  [1]. Li Zhang, Kai Sun, Yan Xing, and Mu Xing, “H6 Transformerless Full-Bridge PV Grid-Tied
Inverters” IEEE Trans. Power Electron., vol. 29, no. 3, pp. 1229 – 1238, March 2014
 [2] S. Araujo, P. Zacharias, and R. Mallwitz, “Highly efficient single-phase transformerless inverters
for grid-connected photovoltaic systems,” IEEE Trans. Ind. Electron., vol. 57, no. 9, pp. 3118–3128,
Sep. 2010
 [3] H. Xiao and S. Xie, “Leakage current analytical model and applica- tion in single-phase
transformerless photovoltaic grid-connected inverter,” IEEE Trans. Electromagn. Compat., vol. 52,
no. 4, pp. 902–913, Nov. 2010
 [4] W. Li, Y. Gu, H. Luo, W. Cui, X. He, and C. Xia, “Topology review and derivation methodology
of single-phase transformerless photovoltaic inverters for leakage current suppression,” IEEE Trans.
Ind. Electron., vol. 62, no. 7, pp. 4537–4551, Jul. 2015