Improved and Hybrid PV

8/12/2019 Improved and Hybrid PV

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Improved and Hybrid PV/Wind Energy System

C. Ravi Chandran1, S. Vasanth Kumar2

1IV Year, EEE University College of Engineering, Anna University, Tuticorin campus, Chennai.2IV Year, EEE, University College of Engineering, Anna University, Tuticorin campus, Chennai.

Email:[email protected],[email protected].

Abstract - This Paper presents an improved and hybrid PV/Wind

energy system along with a new three-input DC - DC boost

converter. Renewable energy sources such as photovoltaic source,

wind sources are used for hybridization of the DC-DC boost

converter. The excessive power demand problems can be solved by

this method. A unidirectional port for the input power sources, a

bidirectional port for a storage element, and an output port for load

are interfaced along with the converter. The method has several

advantages such as bidirectional power flow at the storage port,

simple structure, low-power components, centralized control,

eliminating the need of transformer, low weight, high-stability

working point, independent operation of input power sources, and

high level of boosting. The results and the output are verified bysimulation in MATLAB/SIMLINK for different load condition.

I ndex TermsPhotovoltaic source, wind sources,MPPT, DC DC

boost converter, MATLAB/Simulation software

I.INTRODUCTION

The photovoltaic (PV) has properties such as noiseless, non-

pollutant and little maintenance. But this PV energy depends

on unpredictable shadows, sun irradiation level and ambient

temperature. So, Wind Energy is used as an additional source

which has the advantage of cleanness, high efficiency and

high reliability. Batteries are used for storage purposes andimproves the output power capacity. This forms the Hybrid

system.

Wind and photovoltaic energy are unreliable as they are

inrtermittent. By introducing maximum power point tracking

(MPPT) algorithms and combining them, the above

disadvantage can be overcome. the systems power transfer

efficiency and reliability can be improved significantly. When

any source is unavailable or insufficient in meeting the load

demands, the other energy source can compensate.

The main shortcomings of these traditional integrating

methods are complex system topology, high count of devices,high power losses, expensive cost, and large size. In recent

years, several power conversion stages used in traditional

hybrid systems are replaced by multi-input converters

(MICs), which combine different power sources in a single

power structure. These converters have received more

attention in the literature because of providing simple circuit

topology, centralized control, bidirectional power flow for the

storage element, high reliability, and low manufacturing cost

and size. In general, the systematic approach of generating

MICs is introduced, in which the concept of the pulsating

voltage source cells and the pulsating current source cells is

proposed for deriving MICs. One of the samples of these

MICs is utilized to hybridize PV and wind power sources in a

unified structure. Besides, a systematic method to synthesize

MICs is proposed in [15]. This paper deals with two types of

MICs: in the first type, only one power source is allowed to

transfer energy to the load at a time, and in the second type,

all the input sources can deliver power to the load either

individually or simultaneously.

Two multiple-input converters based on flux additively in a

multiwinding transformer are reported in [17] and [18].

Because there was no possibility of bidirectional operating ofthe converter in [17], and complexity of driving circuits and

output power limitation in [18], they are not suitable for

hybrid systems. In [19], a three-port bidirectional converter

with three active full bridges, two series-resonant tanks, and a

threewinding high-frequency transformer are proposed. In

comparison with three-port circuits with only inductors and

diode bridge at the load side, it gives higher boost gain and

reduced switching losses due to soft-switching operation. A

family of multiport converters based on combination of dc

link and magnetic coupling by utilizing half-bridge boost

converter system features minimum number of conversion

steps, low cost, and compact packaging. In [21], the input

output feedback control linearization for a dc acbidirectional MIC composing a high-frequency isolating link

transformer, two half-bridge boost converters at the input

ports and a bidirectional cycloconverter at the output port is

proposed. In [22][24], three MICs are proposed based on

structure of the dcdc boost converter. The dcdc boost

converter in [22] is useful for combining several energy

sources whose power capacity or voltage levels are different.

The multi-input dcdc converter has the capability of

operating in different converter topologies (buck, boost, and

buckboost) in addition to its bidirectional operation and

positive output voltage without any additional transformer. A

three-input dcdc boost converter can combine a PV, an FC,

and a battery in a simple unified structure. A comprehensivepower management algorithm is realized in order to achieve

maximum power point tracking (MPPT) of the PV source and

set the FC in its optimal power operation range. A three-port

isolated full bridge topology is proposed in [3] for hybrid

FC/battery system, which its aim is feeding a small

autonomous load. This topology gains the advantage of

bidirectional power flow due to the active full-bridges in each

port.
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II.

DESCRIPTION OF IMPROVED SYSTEM

The given block diagram consists of two Input stage solar,

Wind and Bidirectional storage Battery, Multi input DC- DC

Boost converter, MOSFET /IGBT driver stage, Logic Stage,

Inverter and load. The solar panel acts as one of source to the

DC-DC converter. The DC output from the solar panel is

given at one port of the integrated four port DC-DC converter.

By switching ON and OFF the power devices the DC input is

transferred to the inverter.

Fig 1.Functional Block diagram of Hybrid System

The system has 4 ports. The first port is solar power acts as an

port and the second port is DC output from the rectifier

supplied form the wind mill act as another port. Battery acts

as an another port and also act as storage port. All this port

supply the power to the DC-DC converter. Load port act as an

fourth port. The bi-directional storage port battery is used to

supply power as well as act as storage and save excess power.

The DC-DC converter integrates all the power and

synchronizes the supply to the output via inverter. Th DC-DC

converter is an half bridge converter with two diodes and two

switches. According to the MPPT algorithm and PWM pulses

the switching sequences is depend on the power switch ON

and OFF. The output of the DC-DC converter is connected to

an inverter.

The power switches are turned ON and OFF depending on the

switching sequence developed under different source

conditions with different independent duty ratios and the

output DC boosts up the input and the boosted up voltage is

supplied to the inverter. The inverter inverts the supplied DC

power to AC power. The AC power is supplied to the AC

load. The AC load can be for any AC utilities.

The inverter is made of four power switches in which PWM

signals are developed and switching sequences decide ON

and OFF states of power switches in different timing

sequence and these control the power switches and invert the

DC output from the DC-DC converter to AC output and

supplied to the load. The output of the inverter is AC and this

can supply power to utilities with AC supply.

III.

CONVERTER OPERATION

Fig 2.Circuit for DCDC Boost Converter and Load

The above circuit shows the representation of three input DC-

DC converter. From the figure, the converter interfaces two

input power sources v1 and v2, and a battery as the storage

element. Therefore, v1and v2are shown as two independent

power sources that their output characteristics are determinedby the type of input power sources.

The RL is the load resistance, which can represent the

equivalent power feeding an inverter. Four power switches S 1,

S2, S3, and S4 in the converter structure are the main

controllable elements that control the power flow of the

hybrid power system. The circuit enables the switches to be

independently controlled through four independent duty ratios

d1, d2, d3, and d4respectively.

The converter switches S3 and S4 are turned ON, their

corresponding diodes D3 and D4 are reversely biased by the

battery voltage and then blocked. On the other hand, turn OFF state of these switches makes diodes D3and D4able to

conduct input currents iL1 and iL2. In the improved power

system applications, the input power sources should be

explored in continuous current mode (CCM).The current

ripple of the input sources should be minimized to make an

exact power balance among the input powers and the load.

Assuming the same saw tooth wave form to all the switches

and d3, d4


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Fig 3. Switching state 1: 0< t< d1 T.

In this operation mode, two input power sources v1and v2are

responsible for supplying the load, and battery charging/

discharging is not done. This operation mode is considered as

the basic operation mode of the converter. As clearly seen

from the converter structure, there are two options to conduct

input power sources currents iL1 and iL2 without passing

through the battery path 1: S4D3, path 2: S3D4. In this

operation mode, the first path is chosen therefore, switch S3is

turned OFF while switch S4is turned ON entirely

Fig 4.Switching state 2: d1T< t < d2T.

Fig 5.Switching state 3 (d2T < t < T)

in the switching period (d4 = 1 and d3 = 0). Thus, three

different switching states of the converter are achieved in one

switching period.

Fig 6.Steady-state waveform of converter in first

operation modeSecond power operation

In this operation mode, two input power sources V1

andV2along with the battery are responsible for supplying

Fig 7.Switching state 1: 0 < t < d4T.

the load. Therefore, discharging state of the battery should be

provided in this operation mode. Referring to the converter

topology, when switches S3 and S4 are turned ON

simultaneously, currents iL1and iL2are conducted through the

path of switch S4, the battery, and switch S3which results in

battery discharging. However, discharging operations of the

battery can only last until switches S1 and/or S2 are

conducting. As a result, the maximum discharge power of the

battery depends on duty ratios of d1and d2as well as currents

iL1 and iL2.


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Fig 8.Switching state 2: d4T< t < d1T

Fig 9. Switching state 3: d1T < t < d2T.

Therefore, in order to acquire a desired maximum discharging

power of the battery, the input power sources is designed in

proper current and voltage values. On the other hand,

regulating the discharging power of the battery below

Fig 10.Switching state 4: d2T < t


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Fig 13. Switching state 2 (d3T < t < d1T)

Fig 14. Switching state 3 (d1T < t < d2T)

Fig 15 Switching state 4 (d2T < t < T))

operation mode. As per the converter topology, when

switches S3and S4 are turned OFF, by turning ON switches S1

and S2, currents iL1 and iL2are conducted through the path of

diode D4 , the battery, and diode D3, therefore, the condition

of battery charging is provided. The charging operation of the

battery can only last until switches S1 and/or S2 are

conducting. As a result, the maximum charge power of the

battery depends on duty ratios d1 and d2as well as currents iL1

and iL2 OFF.

Therefore, in order to acquire a desired maximum

charge power of the battery, the input power sources shouldbe designed in proper current and voltage values. On the other

hand, regulating the charging power of the battery below the

Pmax bat.ch can be made by changing the state of only one of

switches S3and S4before switches S1and S2are turned OFF

(according to the assumption d3,d4< min (d1,d2 )). In order to

regulate the charging power of the battery, switch S3 is

controlled by regarding the fact that when switch S3is turned

ON, the charging power of the battery is not accomplished

while its turn-off state make the battery to be charged with

currents iL1and iL2 through the path of D3.

VI. Test Results

A. Test Results for Output Voltage

B.Test Result for Output Current

C. Test Result for battery output

D. Test Result for Solar Energy

E. Test Result for Wind Energy


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VII. Experimental verification

The Graph had shown the output voltage and output

current of the proposed hybrid system. Thus verify the

MATLAB simulation block diagram used in this investigation

is valid for the system used.

IX. Conclusion and future scope

This project multi input DC-DC boost converter is

most efficient with renewable energy resources to meet the

present prevailing energy demand. The output of wind and

solar given to DC DC boost converter improves the quality

of output obtained and also eliminates the requirement offilter and transformer section. Another advantage of this

project is that if any input source is removed off the system

can operate as a stand-alone system providing a continuous

output.

This project will be more suitable to meet the energy

demand in residential and industrial sectors. The size of the

wind turbine can be increased for higher power production.

Similarly the MPPT can also be changed for maximum

power. With Suitable improvement in wind energy generation

and solar power generation the output power can be directly

connected with the grid to meet the energy demand. By also

suitable improvement in the hardware design can also lead to

improved efficiency

X. References

1.Chuang Y. C. and Ke. Y. L., High- efficiency and low-

stress ZVT-PWM DC-to-DC converter for battery charger,

Aug.2008.

2.Chen Y. M., Liu Y. Ch., Hung S. C., and Cheng C. S.,

Multi-input inverter for grid-connected hybrid PV/Wind

power system, May 2007.

3.

Chen Y. M., Liu. Y. Ch. and Wu. F. Y., Multi -input

DC/DC converter based on the multi winding transformer

for renewable energy applications, Jul./Aug. 2002.

4.

Duarte .J. L, Hendrix .M, and Simoes .M.G, Three-port

bidirectional converter for hybrid fuel cell systems, Mar.2007.

5.

Gopinath .R., Kim. S., Hahn, J. H., Enjeti. P. N., Yeary M.

B., and Howze, J. W., Development of a low cost fuel cell

inverter system with DSP control, Sep. 2004.

6.Huang X., Wang. X., Nergaard. T., Lai. J. S., Xu. X., and

Zhu L., Parasitic ringing and design issues of digitally

controlled high power interleaved boost converters, Sep.

2004.

7.

Jiang.W and Fahimi.b, Active current sharing and source

management in fuel cell-battery hybrid power system,

Feb. 2010.

8.

Kato. N, Kurozumi .K, Susuld . N, and Muroyama. S,

Hybrid power supply system composed of photovoltaic

and fuel-cell systems, 2001.

9. Liu. Y. Ch. and Chen. Y.M., A systematic approach to

synthesizing multi input DCDC converters, Jan. 2009.

10. Kwasinski A., Identification of feasible topologies for

multiple-input DCDC converters, Mar. 2010.

11.

Krishnaswami. H and Mohan. N., Three-port series-

resonant DCDC converter to interface renewable energy

sources with bidirectional load and energy storage ports,

Mar. 2009.

12.

Matsuo H, Lin.W, Kurokawa. F, Shigemizu.T, and

Watanabe. N, Characteristics of the multiple-input DC

DC converter, Jun. 2004.

13.

Onara. O. C., Uzunoglu. M, and Alam. M. S., Modeling,

control and simulation of an autonomous wind

turbine/photovoltaic/fuel cell/ultra capacitor hybrid

power system, J.Apr. 2008.

14. Peng F. Z., H. Li, G. J. Su, and Lawler J. S., A new

ZVS bidirectional dcdc converter for fuel cell andbattery application, Jan. 2004.

15.

Rajashekara.K, Hybrid fuel-cell strategies for clean

power generation, May/Jun. 2005.

16.

Reddy. K. N. and Agrawal. V., Utility-interactive

hybrid distributed generation scheme with compensation

featureSep. 2007.

17.

Sarhangzadeh M., Hosseini S. H., Sharifian M. B. B., and

Gharehpetian G. B. Multi-input direct DCAC

converter with high frequency link for clean power

generation systems, Jun. 2011.

18. Thounthong .P, Rael. S, and Davat. B., Control strategy

of fuel cell and supercapacitor association for a

distributed generation system, Dec. 2007.19. Yan L., Xinbo R., Dongsheng Y., Fuxin L. Synthesis of

multiple-input DC/DC converters, Sep. 2010.

20.

Tao.H, Kotsopoulos.A, Duarte J. L., and M. A. M.

Hendrix, Family of multiport bidirectional DCDC

converters, 2006

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Improved and Hybrid PV