Inverter Interfacing With PV System And Grid Environmental Sciences Essay

This undertaking is intended to plan Multilevel Inverter Topology for Grid Connected PV Systems. In this undertaking, different multilevel inverter topologies have been focused and analyzed to obtain the wave form which is close to sinusoidal wave form with the most efficient topology. Inverters are of alone importance in modern power industry. This chapter shall be devoted to give an overview of the capable country, subject, background of undertaking, initial study done, purposes, aims of making this undertaking and a job treatment.

1.2 Background of Project

Inverters are the electronic circuits which convert District of Columbia to ac. An inverter transportation power from a District of Columbia beginning to an ac burden. The aim of an inverter is to make an ac electromotive force when a District of Columbia electromotive force is available. Inverters are used in applications like uninterruptible power supplies, adjustable velocity Acs motor thrusts and running ac contraption from battery [ 1 ] . The transition is achieved by proper control known as transition of the inactive power switches provided by the switches agreement or topology. The dc beginning can be either current or electromotive force beginning therefore spliting the inverter household into two chief groups [ 2 ] .

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Voltage Source Inverters

Current Source Inverters

The electromotive force beginning inverters ( VSI ) usage changeless electromotive force beginning provided by a electromotive force beginning rectifier and a capacitive District of Columbia nexus to bring forth a switched electromotive force wave form at the end product with a cardinal electromotive force constituent with variable frequence, stage and amplitude that matches a coveted mention electromotive force. VSI are the most common power transition systems in DC – AC powered applications peculiarly in low and medium power either it is individual or three stage system [ 2 ] .

The current beginning inverters on the other manus, usage changeless current beginning provided by controlled current beginning rectifier and an inductive District of Columbia nexus to bring forth a switched current wave form with adjustable frequence, stage and amplitude. The end product electromotive force in this inverter is defined by the current burden which is normally really sinusoidal for resistive inductive tonss like motor thrusts. The chief drawbacks of the CSI are the current harmonics which needs to be mitigated with capacitive end product filters [ 2 ] .

By utilizing the above techniques, different signifiers of inverters including Half Bridge VSI, Full Bridge VSI, Multilevel Inverters, PWM Current Source Inverters can be designed.

1.3 Initial Survey

The demand for renewable energy has increased significantly over the old ages because of deficit of fossil fuels and nursery consequence. Among assorted types of renewable energy beginnings, air current and solar energy have become really popular. The ground is that these two energy resources are available in immense sum in about all the parts of the universe. Due to achievement in modern power electronics, the air current and solar energy are really demanding. Photovoltaic beginnings are used today in many applications because of being pollution and care free. Solar energy demand is turning systematically by 20 – 25 % per annum over the past 20 old ages because of diminishing cost and monetary values. In a solar system, the exposure Gur inverter is the bosom of system is used to change over dc power obtained from the panels into ac power to be fed into the grid [ 4 ] . The basic apparatus used for solar system is shown in the figure below

Figure.1: Inverter interfacing with PV system and Grid

The figure above illustrates the schematic of a PV system used to bring forth electricity. The energy produced by sunshine is absorbed by the solar panels. Solar panels are connected in combination of series and parallel to obtain coveted electromotive force and current degree. The end product dc beginning from the solar panel is fed into power electronic circuits. The power electronic circuits comprises of two of import circuits i-e the charge accountant and inverter. The map of charge accountant is to command the charging electromotive force and current degree which are to be used to bear down battery bank. The end product from the battery bank is provided to the multilevel inverter for change overing it into ac electromotive forces. This ac electromotive force supply is eventually fed into the power grid for use. The demands of renewable electrical power systems include stabilisation, transition and version, finding maximal efficiency of the PV faculty and ciphering storage or battery demands.

The initial study is conducted utilizing cardinal abstracts, diaries, books, study studies and is described with the relevant information. The IEEE articles written by different bookmans and professors are used to compose interim study. The books used to compose interim study includes Power Electronics by Muhammad Haroon Rashid, Power Electronics and Motor Drives by Bogdan M. Wilamowski and J. David Irwin, Power Electronics by Daniel W. Hart. The articles from the IEEE used can be seen from the list of mentions.

1.4 Aim

The purpose of working on this undertaking is to plan a multilevel inverter with every bit much degrees as possible inorder to obtain the end product wave form near to sinusoidal.

1.5 Aims

To accomplish above purpose, the undermentioned aims are set

Understanding the topologies for planing multilevel inverters

Deciding figure of degrees

Planing circuit

Imitating circuit in PSPICE package

Hardware execution

The purpose described above can be achieved by following the aims one by one and undertaking program for the whole term.

Chapter 2

2.1 Multilevel Inverters

The multilevel inverters have drawn a enormous involvement in the current power industry. They present a new set of characteristics that are good suited for usage in reactive power compensation. With the aid of multilevel inverter, it is easier to bring forth high power, high electromotive force inverter with the multilevel construction due to exchanging technique used. In high power and high electromotive force applications, the two degree inverters have some restrictions in operating at high frequence chiefly due to exchanging losingss and restraints of device evaluations. Furthermore, the semiconducting material exchanging devices should be used in such a mode as to avoid jobs associated with their series parallel combinations which are necessary inorder to obtain capableness of managing high electromotive forces and currents [ 3 ] . There are figure of advantages of utilizing multilevel convertors as given below [ 1-4 ]

They are suited for medium to high power applications

Due to minimum switching frequence, the efficiency of multilevel convertors is really high i-e greater than 98 %

Multilevel convertors can better the power quality and dynamic stableness for public-service corporation systems

The shift emphasis is less

These type of inverters have low Electromagnetic Intervention

Multilevel convertors are an ideal interface between a public-service corporation and renewable energy resources like photovoltaic systems or fuel cells

As the Multilevel inverters have modular and simple construction, they can be stacked up to an limitless figure of degrees

2.2 Topologies for Multilevel

Multilevel inverters can be divided into big figure of topologies, but the most common multilevel inverter topologies includes rectifying tube clamped or Impersonal point clamped convertors, winging capacitance convertors and cascaded H span convertors. The other topologies include Multiple Transformer, Multiple Source, Multiwinding Transformer and Modular Topology. All the above topologies have different constellation from each other. They differ in individual beginning input, low frequence shift, Ability to feed tonss with DC degree constituent, Implementation of high declaration wave forms, Bi-directional operation and I/O isolation [ 5 ] . The figures below shows the constellations described

Figure.1: Impersonal Point Clamped, Flying capacitances, Cascade H- Bridge [ 5 ]

The figure above illustrates the NPC, Flying capacitances and Cascade H -Bridge topologies which can be used to plan multilevel inverter. The three degree impersonal point clamped inverter was the first widely popular multilevel topology which continues to be used extensively in industrial applications [ 6 ] . Subsequently on, this type of inverter was generalized for greater figure of degrees utilizing the same construct of rectifying tube clamped electromotive force degrees which resulted in the current appellation of a rectifying tube clamped converter [ 7 ] . The three degree winging capacitance topology can be considered as a good option to get the better of some of the drawbacks in NPC [ 8 ] , [ 9 ] . In this topology, extra degrees and electromotive force clamping is achieved by agencies of capacitance that float with regard to the District of Columbia beginnings mention. This type of topology does non necessitate extra clamping rectifying tubes and provides excess switch provinces which can be used to command the capacitances charge even under tonss with the District of Columbia degree [ 10 ] . The cascade H-Bridge convertor topology is composed of several H-Bridge convertors connected in cascade connexion. The cascade topology allows the usage of District of Columbia beginnings with different electromotive force values and high declaration multilevel wave forms can be achieved by utilizing comparatively low figure of constituents [ 11 ] , [ 12 ] . In add-on to this, District of Columbia beginnings can be added or subtracted inorder to increase the figure of end product degrees. Although the original cascaded topology requires several stray District of Columbia beginnings, in some systems they may be available through batteries or Photo Voltaic panels. Thus it can be used to implement high efficiency transformer less inverters [ 13 ] , [ 14 ] . The other topologies which can be used for multilevel inverters are shown below in the figure

Figure 2.2: Multiple Transformer, Multiple Source, Multiwinding Transformer [ 5 ]

The figure above illustrates the multilevel transformer, multiple beginning and multiwinding transformer topologies for multilevel inverters. A multiple transformer topology is composed of two cells. It is similar to the cascaded H- span topology but the end products of the isolation transformers are cascade alternatively of straight cascading the H- span outputs. As a consequence of this, merely one District of Columbia beginning is required for such inverters. There are commercial inverters in the market that are based on this topology [ 15 ] , [ 16 ] . In pattern these inverters have proved to be robust and dependable. One disadvantage of this topology is that it requires several low frequence transformers. The multiple beginning inverters use several stray District of Columbia beginnings to bring forth a rectified multilevel wave form which is converted into an ac electromotive forces [ 17 ] , [ 18 ] . In pattern, the multiple beginning topology is one of the most efficient multilevel topologies presently available. For more than ten old ages, it has been tested in some Renewable Energy Sources and the end product consequences have proved it to efficient, robust and dependable [ 19 ] . The disadvantage of this type of topology is the fact that it requires several dc beginnings and does non supply I/O isolation. Another type of topology shown in the figure above is multiwinding transformer topology. This topology can be considered as a fluctuation of the multiple beginning topology. Unlike other topologies, this topology requires merely a individual District of Columbia input which is achieved utilizing multiwinding line frequence transformer. It provides I/O isolation every bit good. This type includes merely one transformer, therefore a high efficiency can be achieved. The sum-up of all the features of most common multilevel topologies discussed above and the specifications for specifying a high public presentation battery inverter are shown in the tabular arraies below

2.3 Features of the topologies

The features of all the above multilevel topologies can be seen with the aid of tabular arraies below. By utilizing these tabular arraies, we can compare the characteristics of multilevel inverters different from one another.

S.No.

Topology

M1

M2

M3

M4

A1

A2

1

Diode clamped

Yes

Yes

No

No

Yes

No

2

Flying Capacitor

Yes

Yes

Yes

No

Yes

No

3

H – span ( Isolated Dc Source )

No

Yes

Yes

Yes

Yes

No

4

H – span ( multi weaving XFMR )

Yes

Yes

Yes

Yes

No

Yes

5

H – span ( +isolated dc/dc )

Yes

No

Yes

Yes

Yes

Yes

6

Multiple Transformer

Yes

Yes

Yes

Yes

Yes

Yes

7

Multiple Source

No

Yes

Yes

Yes

Yes

Yes

8

Multi weaving transformer

Yes

Yes

Yes

Yes

Yes

Yes

9

Modular

Yes

Yes

No

Yes

Yes

No

Table 2.3: Summary of the features of the most common multilevel topologies [ 5 ]

S.No.

Id.

Inverter Features

Precedence

1

M1

Single beginning input

( Required by standard design )

Mandatary

2

M2

Chiefly based on low frequence exchanging

( Low frequence is necessary to accomplish maximal efficiency )

Mandatary

3

M3

Capable to feed tonss with DC degree constituent

( Like grid, it is desired that SARES must be capable to back up tonss )

Mandatary

4

M4

Suitable to implement high declaration wave form

( The usage of filters for low frequence wave forms is non practical )

Mandatary

5

A1

Bi-directional ( 4-quardrant operation )

( For bettering hardiness, optional as battery courser can be added )

Optional

6

A2

Input – End product Isolation

( Assures more flexibleness )

Optional

Table 2.4: Specifications for specifying a high public presentation battery inverter [ 5 ]

The tabular arraies above illustrate the sum-up of the most common topologies which can be used for planing multilevel inverter. In the tabular arraies, the inverter features can be seen highlighted with M1aˆ¦ M4 and A1, A2. The handiness of certain characteristics in a peculiar inverter and mandatary or optional features may differ them from others.

2.4 Experimental / Investigation methods to be adopted

With the aid of comparing shown in the tabular arraies, the best inverter topology with maximal efficiency and maximal figure of degrees can be selected for the undertaking. An appropriate experimental method like fourier analysis will be adopted to mensurate the harmonics constituents, circuit simulation utilizing PSPICE, efficiency of inverter will be calculated further.

Chapter 3

3.1 Simulation of Multilevel inverter

Simulation is an of import portion for any undertaking which needs to be completed successfully with desired results. There are many types of electronic packages like Proteus, Matlab, Power universe etc. which can be used to plan circuit and execute simulation to detect the consequences achieved. The simulation of this undertaking will be performed on “ PSPICE ” . With the aid of latest version of this package “ OrCAD16 ” , many new characteristics can be used to execute simulation. Initially the proposed inverter circuit will be designed. The circuit will be simulated to detect different parametric quantities of the inverter given below

End product wave form

Entire Harmonics Distortion

Fourier Analysis

Number of degrees or stairway

Planing appropriate filter

The above parametric quantities of the multilevel inverter circuit can be readjusted harmonizing to the demand.

3.2 Design of a 3 – I• inverter on PSPICE ( An Example )

A three stage multilevel inverter circuit diagram designed in SPICE is shown as an illustration below

Figure 3.1: Multilevel inverter simulation in PSPICE

The figure above illustrates the design of three stage multilevel inverter circuit with the add-on of filter to minimise harmonics deformation. The Fourier analysis of circuit is shown under following bomber header.

3.3 Fourier Analysis

The Fourier analysis of a multilevel inverter designed in the above illustration is shown below in the figure

Figure 3.1: Fourier Analysis of the designed inverter

The figure above illustrates the fourier analysis of the circuit designed as an illustration. From the analysis we can see that the cardinal constituent of the end product wave form is high whereas the uneven multiples of the harmonics constituents are pushed frontward to cut down the consequence of harmonics deformation every bit much as possible. This is in fact the intent of planing multilevel inverter.

3.4 Hardware Implementation

After the successful completion of choosing the best multilevel inverter topology, planing maximal figure of degrees or stairway, package simulation and analysis, eventually the circuit can be implemented practically. The of import equipments which are used to do hardware are listed below

Three Phase step up transformer

Digital Oscilloscope

Printed Circuit Board

Mosfets, Capacitors, Diodes, Resistors, Inductors

Soldering Fe station

Chapter 4

4.1 Time Plan for thesis

Every undertaking should be completed in a given clip period inorder to do it successful and worthwhile. The completion is related with the clip tabular array or path map designed to accomplish aims. The clip program which will be adopted by me to finish the thesis is given in the signifier of Gantt Chart below

Figure 4.1: Dissertation Plan Gantt Chart

The Gantt chart of the proposed program is displayed in the figure above. The chart shows that the initial procedure of choosing the thesis subject, initial talk research has been done. The unwritten presentation has been delivered on 25th of May and after that twenty-four hours the interim study has been started as it is to be submitted on 1st of June. After study entry on 1st of June, the chief stage of thesis will get down. During this chief stage, the program for working will be set, some past research work will be studied, IEEE documents will be given necessary attending and therefore the efficient multilevel inverter topology will be selected for execution. Once the topology has been selected, the circuit design will be analyzed utilizing PSPICE package. With the aid of this package the end product wave form, Harmonics Distortion, figure of degrees, filter at end product and Fourier analysis of the circuit will be observed. Meanwhile, the posting will be designed and presented on 4th of July. After the posting presentation, the stuff will be refined and proper thesis authorship will get down and go on till the entry. The hardware execution will get down from 30th of August and will last for about 4 to 5 hebdomads. The hardware execution will hopefully complete before September. After hardware execution, the study will be finalized with images, consequences, graphs etc. and eventually entry will take topographic point in hebdomad 16 of Term 3.

4.2 Deliverables or specific results

The particular outcomes which are expected to be obtained after making this undertaking successfully are given below

Choosing the most efficient topology for Grid connected multilevel inverter

Planing multilevel inverter with maximal figure of degrees / stairway

Planing sensible circuit with minimal figure of Switch overing devices like Mosfets

Less complicated circuit will be designed so that it will be easier to implement

Appropriate usage three stage transformer with protection circuit

Filter circuit will be designed to do sinusoidal wave form

4.3 Decision

The new progress power electronics plays a critical function in the integrating of renewable energy beginnings into the grid. It should be possible to develop the power electronics interface for the highest projected PV system evaluation. Most of the renewable energy beginnings can ot be used straight. The energy produced by them is stored in the battery bank to get the better of the intermittency job normally found in renewable beginnings. The grid system requires the most efficient topology for multilevel inverters. As the current demand would be high, the best topology which can be used is multi weaving transformer. The multi weaving topology for inverters offers all the characteristics required for grid because it is dependable, efficient and offers system protection every bit good. Further probe is still required to detect more characteristics.

Mentions List

[ 1 ] Daniel W. Hart, Power Electronics, The McGraw Hill Companies,

[ 2 ] Bogdan M. Wilamowski and J. David Irwin, The industrial Electronics Handbook, Power Electronics And Motor Drives, Second Edition, CRC Press Taylor and Francis Group, LLC

[ 3 ] Muhammad H. Rashid, Power Electronics Circuits, Devices and Applications, Third Edition, Pearson Education International

[ 4 ] V.G. Agelidis, D.M. Baker, W.B. Lawrance and C.V. Nayar, “ A multilevel PWM inverter topology for photovoltaic applications, ” in proc. IEEE ISIE, Guimaraes, Portugal, 1997, pp. 589 – 594.

[ 5 ] Sergio Daher, Jurgen Schmid, and Femando L.M Antunes, “ Multilevel inverter Topologies for base Alone PV Systems ” IEEE Transactions on industrial electronics, VOL. 55, NO.7, JULY 2008.

[ 6 ] A. Nabae, I. Takahashi, and H. Akagi, “ A new neutral-point clamped PWM inverter, ” in Proc. IEEE Ind. Appl. Soc. Conf. , 1980, pp. 761-766.

[ 7 ] N. S. Choi, J. G. Cho, and G. H. Cho, “ A general circuit topology of multilevel inverter, ” in Proc. IEEE Power Electron. Specialists Conf. , Cambridge, MA, 1991, pp. 96-103.

[ 8 ] J. Huang and K. A. Corzine, “ Drawn-out operation of winging capacitance multilevel inverters, ” IEEE Trans. Power Electron. , vol. 21, no. 1, pp. 140-147, Jan. 2006.

[ 9 ] S. Sirisukprasert, “ Optimized harmonic stepped-waveform for multilevel inverter, ” M.S. thesis, Dept. Elect. Eng. , Virginia Polytechnic Inst. State Univ. , Blacksburg, VA, 1999.

[ 10 ] N. Celanovic, “ Space vector transition and control of multilevel convertors, ” Ph.D. thesis, Virginia Polytechnic Inst. State Univ. , Blacksburg, VA, 2000.

[ 11 ] S. Mariethoz and A. Rufer, “ Design and control of asymmetrical multilevel inverters, ” in Proc. Int. Conf. Ind. Electron. Control Instrum. , Seville, Spain, 2002, pp. 840-845.

[ 12 ] J. Dixon and L. Moran, “ High-level multistep inverter optimisation utilizing a minimal figure of power transistors, ” IEEE Trans. Power Electron. , vol. 21, no. 2, pp. 330-337, Mar. 2006.

[ 13 ] M. Calais, V. G. Agelidisb, and M. S. Dymondc, “ A cascaded inverter for transformerless single-phase grid-connected photovoltaic systems, ” Renew. Energy, vol. 22, no. 1, pp. 255-262, Jan. 2001.

[ 14 ] O. Lopez, R. Teodorescu, and J. D. Gandoy, “ Multilevel transformerless topologies for single-phase grid-connected convertors, ” in Proc. IEEE Ind. Electron. Conf. , Paris, France, 2006, pp. 5191-5196.

[ 15 ] “ SW Series Inverter/Chargers, ” Owner ‘s Manual, Trace Eng. Company Inc. , Arlington, WA, Sep. 1999.

[ 16 ] Sine Wave Plus Inverter/Charger Owner ‘s Manual, Xantrex Technol. Inc. , Burnaby, BC, Canada. Sep. 2003. 976-0043-01-02 Rev B. [ Online ] . Available. www.xantrex.com

[ 17 ] J. Schmid et al. , “ Inverter for change overing a direct electromotive force into an alternating electromotive force, ” U.S. Patent 4 775 923, Oct. 4, 1988.

[ 18 ] F. Kininger, Photovoltaic Systems Technology. Kassel, Germany: Universitat Kassel, Institut fur Rationelle Energiewandlung, 2003.

[ 19 ] Fraunhofer Institut Solare Energiesysteme-ISE, Compendium of Projects on Rural Electrification and Off-Grid Power Supply, Freiburg, Germany, 2001. [ Online ] . Available: www.ise.fhg.de

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