S.Prakash , N.P.Gopinath , J.Suganthi · 2018. 3. 15. · S.Prakash 1, N.P.Gopinath 2, J.Suganthi 3...
Transcript of S.Prakash , N.P.Gopinath , J.Suganthi · 2018. 3. 15. · S.Prakash 1, N.P.Gopinath 2, J.Suganthi 3...
A GRID TIED MODIFIED SYMMETRICAL CASCADED H-BRIDGE BOOST
INVERTER WITH PV SYSTEM USING MPPT
S.Prakash1, N.P.Gopinath2, J.Suganthi3
Department of EEE, Aarupadai Veedu Institute of Technology,
Vinayaka Mission’s Research Foundation.
Paiyanoor, Chennai, India.
[email protected], [email protected], [email protected]
Abstract:
With the fast entrance of photovoltaicassociated framework in modern and business
application, it is basic to enhance the effectiveness and upgrade the usage of PV power
control system. In this paper PV array with modified symmetrical cascaded H-bridge inverter
is developed.This work is based on integration and operation of a single phasemodified
symmetrical cascaded H-bridge with bidirectional switches.The boost converter with
maximum power point trackers (MPPT) technique is proposed to achieve the maximum
power output of the PV array. The proposed grid connected inverter with PV array is
simulated using MATLAB/SIMULINK and results are discussed in detail.
Keywords:Symmetrical Multilevel Inverter, Photovoltaic, Boost Converter, Maximum Power
Point Tracking
I. Introduction
Since energy assets and their usage have a noticeable issue of this century, the issues
of common asset consumption, natural effects, and the rising interest for new energy assets
has been talked about intensely as of late. Various forms of renewable energy sources are
available to make the environment as carbon-free pollution and the sources are solar, wind,
biomass, geothermal etc. are paid more attention to researchers and scientists.Amongst
different kinds of sustainable power sources, solar energy has turned out to be extremely
famous and requesting because of headway in control of power electronic techniques. Solar
technologies tap specifically into the unending energy of the sun and utilize that energy to
create heat, light, and control.
The energy created from solar cell transformation framework relies on the solar
illumination whereas the electrical lattice requires consistent voltage and recurrence. Hence
appropriate power electronic interface must be given between the sustainable power source
and the network for stable operation. Solar cell establishments include the utilization of
numerous solar boards or modules, which can be associated in arrangement or in parallel to
give the coveted voltage level to the inverter.
Keeping in mind the end goal to associate Renewable Energy Source to the
framework, two phases of energy change are utilized. The principal organize is to support up
the low voltage yield of Renewable Energy Source and to track its Maximum Power Point
(MPP), whereas the second stage is utilized to change over DC into AC wave as required by
the grid. To build the effectiveness of the network associated sustainable power source
International Journal of Pure and Applied MathematicsVolume 118 No. 5 2018, 833-843ISSN: 1311-8080 (printed version); ISSN: 1314-3395 (on-line version)url: http://www.ijpam.euSpecial Issue ijpam.eu
833
frameworks single stage help inverters are proposed in the researcher. Single stage control
change technique decreases the losses, thereby expanding the proficiency, yet it experiences
disadvantages like higher Total Harmonic Distortion (THD) at the yield voltage which in the
long run builds the channel measure, thereby expanding the cost and size of the aggregate
framework.
To enhance the harmonic profile of the yield voltage of the inverter Multilevel
Inverters (MLIs) are recommended different researches. MLIs have almost sinusoidal yield
voltage and current waveforms with an enhanced harmonic profile, less voltage stress in
power electronic switches because of decreased voltages, bring down switching losses when
contrasted with regular three-level inverters, reduced the filter circuit, and lessened
electromagnetic interferences. As of late different MLIs are proposed in the researches and
the regularly utilized categories are diode-clamped, flying capacitor, cascaded H-bridge and
hybrid or modified H-bridge Multilevel Inverter . The cascaded H-bridge multilevel inverter
topology requires a different DC source for each H-bridge with the goal that high power or
potentially high voltage that can come about because of the blend of the various modules in a
multilevel inverter would support this topology. MLIs are further grouped into symmetrical
and asymmetrical types. This paper presents a Modified Symmetrical Cascaded H-Bridge
MLI (MS-CHBMLI) topology reasonable for sustainable power sources. The proposed
inverter is equipped for creating five levels with two bidirectional DC sources and six power
semiconductor controlled switches. From the six power semiconductor devices, two power
semiconductor devices are bi-directional and four devices are unidirectional devices. The
proposed inverter has many focal points like basic in structure, versatile for coordinating
Renewable Energy Source with the framework, bring down THD and the lesser number of
semiconductor switches.
II Proposed Modified Symmetrical Multilevel Inverter
In this proposed configuration comprises of two bidirectional switches along with
freewheeling diode added to the cascaded H-bridge circuit and the proposed concept diagram of solar
PV array with grid connected modified symmetrical multilevel inverter as shown in Fig.1. The
existing topology has been eight switches which is possible for creating the five levelsand it is or
asymmetrical or symmetrical kind. Hence In this topology proposed in has two bidirectional switches
which are equipped for producing five levels and the total number of switches is reduced from eight to
six.The traditional cascaded H-bridge inverter has the issue of capacitor voltage adjusting when
encouraged to high power loads. The modified symmetrical MLI proposed in this paper requires only
two bidirectional switches to generate five level output voltage or current waveform and also this
topologysmooth the progress of the issue of capacitor voltage balancing.
International Journal of Pure and Applied Mathematics Special Issue
834
Fig.1. Proposed PV connected Modified Symmetrical Cascaded H-Bridge Multilevel Inverter
(a) (b)
(c) (d)
International Journal of Pure and Applied Mathematics Special Issue
835
(e) (f)
Fig.2 Operating modes and current direction of proposed inverter a)& b) Mode-1 c) & d).Mode-2 e)
Mode-3 and f) Mode-4.
In order to generate the stepped waveform output wide range, the modified symmetrical
cascaded H-bridge multilevel inverter topology is proposed, shown in Fig. 1. The proposed topology
includesone H-bridge circuit along with connected auxiliary unit of bidirectional power
semiconductor switch A1 and A2through aline inductor and grid terminals. The operating mode of
proposed inverteris basically two groups.One is for with auxiliary circuit and the modes of operations
are Mode-1 & 2.The second group is without auxiliary circuit and their operating modes are Mode-3
& 4. The proposed topology operated as a traditional cascaded H-bridge inverter circuit when itsmode
of operation at Mode-3 and 4. The isolated d.c sources are symmetrical or equal value in the proposed
topology.
The fig.2 shows that the operating modes of proposed topology and their current direction in
the circuit are indicated as dark blue lines with arrow direction. The binary logic switching operation
of proposed MS-CHBMLI is as shown in table.1.The proposed concept can be extend any number of
level with same type of operating modes of operation.
Table 1. Binary Switching Table of proposed inverter
Inverter
Operation
Output
Voltage S1 S2 S3 S4 A1 A2
Mode-3 +2Vdc 1 1 0 0 0 0
Mode-2 +Vdc
1 0 0 0 1 0
0 1 0 0 0 1
Mode-0 0 0 0 0 0 0 0
Mode-2 -Vdc
0 0 1 0 0 1
0 0 0 1 1 0
Mode-4 -2Vdc 0 0 1 1 0 0
The output voltage generated at group one operating mode is
𝑣𝑜 = ∑ 𝑆𝑥4𝑥=0 = 𝑘𝑉𝑑𝑐 {
𝑓𝑜𝑟𝑘 = +1 if x <= 2𝑓𝑜𝑟𝑘 = −1 if x >= 3
(1)
where, S is the main H-bridge power semiconductor switches turn on / off condition
International Journal of Pure and Applied Mathematics Special Issue
836
x is the number power semiconductor switches
k is the polarity of output voltage at grid
III Maximum power point tracking with Grid
The proposed modified symmetrical cascaded H-bridge multilevel inverter can be a best
suitable for grid-connected green energy applications. The operating point of photovoltaic module is
determined by solar rays, the temperature of PV component and the amount of resistance added as a
load. For a given cell temperature and solar rays, there can be an exclusive operating point of the PV
array in its PV curve with maximum end result electricity. Henceforth Maximum Power Point
Tracking (MPPT) is important in PV arrays to be able to achieve maximum power from it regardless
of the load and environmental climatic conditions.Mostly, the DC-DC boost converter topology can
be used next to PV component for two primary reasons. The principal reason is to monitor the
maximum power point (MPP) and the supplementary reason is to improve up the lower result voltage
of PV component to ahigher level. Thus the DC-DCboost converters duty pattern would depend on
the MPPT algorithm. In this way when the environmental conditions shift MPPT algorithm changes
the duty cycle which thus increases or reduces the output generated voltage of the boost converter.
However the DC input voltage of the inverter must have a rigid value it is associated with the grid.
Consequently DC-DC boost converters are being used in cascade, some may be to track the MPP and
the other is to keep the DC-link voltage to a rigid value.
3.1 DC-DC Boost Converter
Open loop construction of DC-DC converter will most likely lead to poor efficiency. Hence
instantaneously the output of the converter is evaluated and with a given reference, and the duty cycle
of the switch should be altered. The boost converter is perfect for boost approach to treatment with
solar cell voltage as type source as shown in fig . For widely open loop simulation the input voltage to
the boost converter is extracted from the solar cell. The output of converter governed voltage will be
obtained. The duty cycle of the converter switch is determined by,
𝑑𝑏 = 𝑉𝑑𝑐−𝑉𝑝𝑣1
𝑉𝑑𝑐 (2)
Fig.3 DC-DC boost converter with MPPT
International Journal of Pure and Applied Mathematics Special Issue
837
The Perturbation and Observation(P&O) control algorithm is used in order to achieve
maximum power from PV solar panel. . In the event that the most extreme power level of a PV array
is higher than the power rating of an MPPT, the two MPPTs will be in parallel operation to function
as a single MPPT. Hencethese systems have need of an online arrangementfor ensure and to verify the
connection kinds of the two MPPTs, independentlyor in parallel. Additionally, if the two MPPTs are
in parallel operation, a uniform current control scheme is familiar with correspondingly flow the PV-
array output current to the two MPPTs. From the above relations, the P&O algorithm tracks maximum
power output through the controller based on the output of PV array.The maximum output current is
achieved when the solar array output current 𝑖𝑝𝑣 is equal to the inductor 1 output current 𝑖𝑚.Then the
expression for maximum power output of PV array output is
𝑃𝑚 = 𝑣𝑝𝑣𝑥𝑖𝑚 (3)
Where, 𝑣𝑝𝑣- PV array across the output voltage in volts
𝑖𝑚-maximum current through the inductor 1 of pv array circuit
3.2 Grid Interconnection
Solar PV array with MS-CHBMLI is interconnected with grid when achieving the amplitude
of voltage, frequency and phase angle are same.This ought to be conceivable disturbance affirmation
in regards to the system by identifying the grid voltage in a Phase Locked Loop (PLL).The grid
voltage angle position is determined from PLL output.The output of PLL signal is reference voltage
signal and it generates the gating signal to the MS-CHBMLI power semiconductor switches by multi
carrier sinusoidal pulse width modulation technique.The output voltage of inverter is generated based
on the grid voltage.The phase angle difference is calculated and this is controlled to make a zero for
faster interconnection between the grid and inverter.The power flow through the inverter to grid based
on delay angle is
𝑃 =𝑉𝑖𝑉𝑔
𝑋𝑙𝑠𝑖𝑛𝛿 (4)
where𝑉𝑖is the inverter output voltage,
𝑉𝑔is the interconnected grid voltage,
𝑋𝑙isthe medium impedance,
and δ is the angle between grid andinverter
IV Simulation Results
The proposed work is analyzed using Matlab simulation. It is shown in figure. The PV
modules output voltages are fed to the single phase inverter through boost converter. The
MPPT P&O algorithm extracts maximum power from the PV system.
International Journal of Pure and Applied Mathematics Special Issue
838
Fig 4. Simulation diagram of PV system
Fig 5. Input voltage from the PV system
The figure 5 shows the input voltage from the PV system. The PV output voltage is in
oscillatory nature due to temperature and irradiation variations. This voltage is given to the
boost converter. The MPPT algorithm extracts maximum power from the solar system.
Fig 6. Output voltage of the boost converter
The figure shows the output voltage of the boost converter. The MPPT algorithm
maintains constant voltage to the single phase five level inverter topology. The new topology
converter dc voltage into five level AC voltage.
International Journal of Pure and Applied Mathematics Special Issue
839
Fig 7. Output voltage of the five level inverter
The figure shows the five level inverter output voltage of the proposed topology. This
has reduce the THD. This voltage is given to the grid using synchronization technique.
Fig 8. Output voltage and current signal in the grid
The figure shows the synchronization of the voltage and current. Both voltage and
currents are in phase here.
International Journal of Pure and Applied Mathematics Special Issue
840
Fig 9. THD value of the proposed grid voltage
The figure shows the THD value of the grid voltage and its satisfies the harmonics
IEEE standard. The proposed five level inverter reduces the total harmonics distortion in the
output voltage.
V Conclusion
This projects develops single phase grid connected PV using reduced number of
switches with five level inverter. The MPPT algorithm extracts the constant ans maximum
power from the PV system. The five level inverter with reduced number of switches
minimize the THD. Switching losses also less in the proposed topology. The multi reference
PWM is used to control the output voltage of the inverter. The synchronization technique
reduce the THD and power quality issues. This paper THD result satisfied the THD
harmonics IEEE standard.
References
[1]. Carrasco, J.M., Franquelo, L.G., Bialasiewicz, J.T., Galvan, E., Guisado, R.P., Prats,
M.A. and Moreno-Alfonso, N.(2006) Power-Electronic Systems for the Grid
Integration of Renewable Energy Sources: A Survey. IEEE Transactionson Industrial
Electronics, vol-53, pp.1002-1016.
[2]. S. B. Kjaer, J. K. Pederson, and F. Blaabjerg, “A review of single-phase grid-
connected inverters for photovoltaic modules,”IEEE Trans. Ind. Appl., vol. 41, no. 5,
pp. 1292-1306, Sep/Oct. 2005.
[3]. K EswaramoorthyandV K Shunmughanaathan, “A Simple And Geometry Based Fast
Space-Vector PWM Technique For 15 Level Cascaded Multilevel Inverter With
Reduction Of Switches”, Asian Journal of Research in Social Sciences and
Humanities,Vol-6,issue-10, pp.2305-2320.
[4]. Eswaramoorthy K, Kavin K.S, Manobala M, Subashini M, ‘Single Phase Thirteen-
Level Inverter using Seven Switches for Photovoltaic systems”, International Journal
International Journal of Pure and Applied Mathematics Special Issue
841
of Modern Trends in Engineering and Research (IJMTER),Vol-2,issue-01,pp.665-
672.
[5]. Calais, M., Agelidis, V.G. and Dymond, M.S. (2001) A Cascaded Inverter for
Transformer Less Single-Phase Grid-Connected Photovoltaic Systems. Renewable
Energy, vol.22, pp.255-262.
[6]. S. M. Silva, B. M. Lopes, B. J. C. Filho, R. P. Campana, W. C.Boaventura,
“Performance Evaluation of PLL Algorithms for SinglephaseGrid-connected
Systems,” IEEE Industry Applications SocietyAnnual Meeting, Seattle, Washington,
October 3-7, 2004, pp. 2259-2263.
[7]. Pandey, N. Dasgupta, A. K. Mukerjee, “A Simple Single-sensor MPPT Solution,”
IEEE Transactions on Power Electronics, vol. 22, no. 2, March 2007, pp. 698-700.
[8]. O. Alonso, P. Sanchis, E. Gubia, L. Marroyo, “Cascaded H-bridge Multilevel
Converter for Grid Connected Photovoltaic Generators with Independent Maximum
Power Point Tracking of each Solar Array,” IEEE Power Electronics Specialist
Conference, 15-19 June 2003, pp. 731-735.
International Journal of Pure and Applied Mathematics Special Issue
842
843
844