International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982 Volume-4, Issue-4, Apr.-2016
1
SRI SUDHA,
2
K. KALYANI,
3
B. SANKARA PRASAD
1
M. Tech Student,
2
Associate professor,
3
HOD and Associate professor
Electrical and Electronic Department, St.Theressa Institute of Engineering and Technology
Abstract- The main focus of this paper is to reduce the number of the components and also to reduce the leakage current of the system. Boost converter is eliminated by using highly presided switches. Even though the boost converter is eliminated the same generated power is transmitted to the grid, as a result the cost the system size can be reduced, losses are minimized and efficiency is improved. Matlab and simulation results of the proposed model and control techniques are presented.
Key words- Reduced Boost Converter, Grid Connected PV System, State Vector Pulse Width Modulation (SVPWM).
I. INTRODUCTION
The rapid depletion of fossil based energy resources such as coal, natural gas and oil together with an effort to reduce CO2 emission into the atmosphere has required a demand for a larger share of clean energy to be produced from renewable energy sources. The sun is the primary energy source that subsequently creates substantial diversity of renewable energy sources on the Earth, However, solar energy that can be collected directly on the
Earth’s surface still accounts for the largest amount of renewable energy compared to all other renewable sources. Therefore, using solar energy could be sufficient for securing the future energy requirements.
In addition, solar energy can be converted directly to electricity using devices called Photovoltaic (PV) cells, this paper presents a solar PV system among the other conventional system due to the following benefits such as absolutely no pollution during energy conversion, having no moving parts thus require negligible maintenance, gives long lifetime typically
20-25 years and it can be installed anywhere including remote areas.
In Section I introduction is carried out, in section II discusses about conventional transformer less grid connected solar photovoltaic system and its applications and disadvantages. In section III proposed model is carried out by overcoming the drawbacks of the conventional model and discussed the applications. In section IV controlling technique using State space vector pulse width modulation over conventional modulation techniques. In section V results
II. TRANSFORMERLESS CONVENTIONAL
GRID CONNECTED PV SYSTEM
In conventional model of transformer less PV system connected to grid shows a diode, which is connected in added in the front of the topology compared to the original structure, to block the leakage current loop during the active vectors and open-zero vectors, of which the CMV V cm
is defined as [4]
V
CM

V aN
 V bN
 V cN
3
V
Nn

V aN
 V bN
3
 V cN
  V
CM
V
Pn
 V
Pn
 V
Nn
 V
Pn
 V
CM
( 1 )
( 2 )
( 3 )
Fig. 1. Conventional Transformerless grid-connected PV system diode.
The voltage between positive P or negative N solar panel and grounded neutral n can be expressed as the possible switching states include six active vectors
(V1–V6 ), two open-zero vectors (V0 ,V7 ), and seven shoot-through zero vectors including one leg shoot through (V a
shoot ,V b
shoot ,V c
Shoot), twolegs shoot through (V ab
shoot ,V ac
shoot ,V bc
shoot) and three-legs shoot through (V abc
shoot). For all the odd active vectors (V
1
,V
3
,V
5
), all the even active vectors (V2 ,V4 ,V6 ), all the open-zero vectors (V
0
,V
7
), and all the shoot-through zero vectors, the common mode voltages (V cm
) and voltages (V
P n
,
V
Nn
) of CL-SSBI and CL-SSBI with an additional diode (CL-SSBI-D) can be derived from (2) and (3), as shown in Table I.
TABLE –I. COMMON-MODE VOLTAGES V
CM
, VOLTAGES V
N n
AND V
P n
IN DIFFERENT
SPACE VECTORS (a) FOR CL-SSBI-D
For convenience, supposing the turns ratio N of the coupled inductor is 2.5, shoot-through zero duty cycle
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International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
D 0 is 0.17, and then boost factor B is 3, according to the bus voltage expression of V b
= BvPN [16], and using the maximum constant boost (MCB) control method realized by space vector-based PWM control
[18], the switching pattern and CMV of CL-SSBI and
CL-SSBI-D in section A1 [see Fig. 2(a)] can be obtained, as shown in Fig. 2(b) and (c), in which Ts is defined as a switching period.
III. PROPOSED MODEL
Fig.2. Proposed model
Figure 2. Shows the proposed model. Solar PV module generates the DC voltage, which is fed to the grid through single stage 3-phase inverter, which converts generated DC supply into AC voltage. Load is connected through breaker.
IV. CONTROLLING TECHNIQUE TO
REDUCE THE NUMBER OF COMPONENTS
Space-Vector Pulse Width Modulation (SVPWM):
Volume-4, Issue-4, Apr.-2016 modulation (TPWM) etc, the importance of this proposed SVPWM technique plays a vital role in three-phase inverters because this technique is mainly implemented based on
 p
. By using SVPWM technique the output voltage enhanced when compared to SPWM technique and also it uses all the states in state vector model i.e. SPWM technique couldn’t use the states (000 and 111) [14]. Because of the two states, this proposed scheme is better than
SPWM technique. SVPWM generates less THD than
SPWM. Maximum fundamental magnitude of
SVPWM controlled inverter is 90.6% and Maximum voltage acquired is 15.5% [14]. Representation of
Space Vector is shown in fig.4. All the peak points of vectors touching with a reference vector, in this manner a circle can be shaped inside the state model.
There are mainly two regions in state model, under modulation, and over modulation. These two regions are relying on modulation index. the power electronic components are greatly reduced In this paper and the same functionality is carried out using this highly controlling technique, and minimizes the power losses by controlling the output of the inverter. Hence precise controlling has been achieved and harmonic content in the output waveforms are greatly reduced as a result total harmonic distortion is THD is less.
V. SIMULINK MODEL
Fig.5. Simulink diagram of proposed system
VI. RESULTS AND DISCUSSION
In order to validate the theoretical analysis, the simulation and experimental tests of the transformerless grid-connected PV system constructed by CL-SSBI and CL-SSBI-D are carried out, respectively. The PV frame and the neutral point of the grid are grounded. The simulation and experimental parameters are shown in Table II.
Fig. 4 shows the simulation results of the gridconnected CL-SSBI system modulated by MCB control. The three-phase
Fig.4. Space Vector Representation
The main aim of SVPWM is to generate the inverter controlling signal in order to modulate the pulses effectively and also to enhance the output performance of the inverter and lessening the power losses. State vector (SV) controlling technique was actually introduced in 1980s. Even though literature presents more and more modulation techniques like sinusoidal modulation (SPWM), triangular Fig.5. DC bus Voltage
Single Stage Power Converter System For Efficient Solar Power Generation
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International Journal of Industrial Electronics and Electrical Engineering, ISSN: 2347-6982
Fig.6. Inverter terminal voltage
Fig.10. Inverter Phase Voltages
Fig.7. Load Currents
Fig.8. Load Voltage and Current
Volume-4, Issue-4, Apr.-2016
CONCLUSION
This paper reduced the number of the components and also reduced the leakage current of the system.
Boost converter is eliminated by using highly presided switches. Even though the boost converter is eliminated the same generated power is transmitted to the grid, as a result the cost the system size can be reduced, losses are minimized and efficiency is improved. Matlab and simulation results of the proposed model and control techniques are presented.
REFERENCES
[1] R. Gonzalez, J. Lopez, P. Sanchis, and L. Marroyo,
“Transformerless inverter for single-phase photovoltaic systems,” IEEE Trans. Power Electron.
, vol. 22, no. 2, pp.
693–697, Mar. 2007.
[2] H. Xiao and S. Xie, “Transformerless split-inductor neutral point clamped three-level PV grid-connected inverter,” IEEE Trans. Power Electron.
, vol. 27, no. 4, pp.
1799–1808, Apr. 2012.
[3] S. V Araujo, P. Zacharias, and R. Mallwitz, “High efficiency single-phase transformerless inverters for gridconnected photovoltaic systems,” IEEE Trans. Ind.
Electron.
, vol. 57, no. 9, pp. 3118–3128, Sep. 2010.
[4] J. M. Shen, “Novel transformerless grid-connected power converter with negative grounding for photovoltaic generation system,” IEEE Trans. Power Electron.
, vol. 27, no. 4, pp. 1818–1829, Apr. 2012.
[5] X. Guo, M. C. Cavalcanti, A. M. Farias, and J. M.
Guerrero, “Singlecarrier modulation for neutral pointclamped inverters in three-phase transformerless photovoltaic systems,” IEEE Trans. Power Electron.
, vol.
28, no. 6, pp. 2635–2637, Jun. 2013.
[6] E. Koutroulis and F. Blaabjerg, “Design optimization of transformerless grid-connected PV inverters including reliability,” IEEE Trans. Power Electron.
, vol. 28, no. 1, pp. 325–335, Jan. 2013.
[7] B. Gu, J. Dominic, J.-S. Lai, C.-L. Chen, T. LaBella, and
B. Chen, “High reliability and efficiency single-phase transformerless inverter for gridconnected photovoltaic systems,” IEEE Trans. Power Electron.
, vol. 28, no. 5, pp.
2235–2245, May 2013.
[8] D. Barater, G. Buticchi, A. S. Crinto, G. Franceschini, and
E. Lorenzani, “Unipolar PWM strategy for transformerless
PV grid-connected converters,” IEEE Trans. Energy
Convers., vol. 27, no. 4, pp. 835–843, Dec. 2012.
[9] M. C. Cavalcanti, A. M. Farias, K. C. de Oliveira, F. A. S.
Neves, and J. L. Afonso, “Eliminating leakage currents in neutral point clamped inverters for photovoltaic systems,”
IEEE Trans. Ind. Electron., vol. 59, no. 1, pp. 435–443,
Jan. 2012.
Fig.9. Grid Voltage and Current
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