Research Article Flexible Mode Control of Grid Connected ...downloads.hindawi.com/journals/jen/2015/152898.pdf · controls reactive power. Grid currents are converted in synchronous

Research ArticleFlexible Mode Control of Grid Connected Wind EnergyConversion System Using Wavelet

Bhavna Jain Sameer Singh Shailendra Jain and R K Nema

MANIT Bhopal 462003 India

Correspondence should be addressed to Bhavna Jain jain bhavna69yahoocom

Received 30 June 2014 Revised 21 January 2015 Accepted 29 January 2015

Academic Editor Ahmet Z Sahin

Copyright copy 2015 Bhavna Jain et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Small wind turbine systems offer services to critical loads during grid faults and also connected back to grid in normal conditionTheconnection of a wind energy conversion system to the grid requires a robust phase locked loop (PLL) and continuous monitoringof the grid conditions such as overvoltage undervoltage overfrequency underfrequency and grid outages This paper describesa flexible control operation to operate a small wind turbine in both stand-alone mode via planned islanding and grid connectedmode as well In particular a proper monitoring and control algorithm is required for transition between the modes A waveletbased energy function is used for detection of grid disturbances as well as recovery of grid so that transition between the modes ismade To obtain good power quality LCL filter is used to reduce ripples PLL is used for synchronization whenever mode changesfrom stand-alone to grid connected Simulation results from a 10 kW wind energy conversion system are included to show theusefulness of the proposed methods The control method is tested by generated gate pulses for single phase bridge inverter usingfield programmable gate array (FPGA)

1 Introduction

Due to awareness for pollution free environment depletion ofconventional energy sources and growing demand of energyworldwide the government of different countries has beenpromoting electricity generation from renewable sourcesRenewable energy sources are becoming an important optionto meet the growing demand of energy and simultaneouslyhelp in controlling of greenhouse gas emission caused by con-ventional energy sources Anothermajor benefit of renewableenergy source is that it can work in stand-alonemode to fulfilthe customer demand and canwork as grid connected systemto supply extra power generated to grid hence increasing thereliability of power supply

Out of all renewable sources wind power generationtechnology has been grown up in the beginning with fewKW to multi-MW capacity wind turbine manufactured andinstalled An attractive idea of universal mode of small windturbine (SWT) has been implemented in which they caneither operate as stand-alone mode or can work in grid con-nected mode [1 2] Small wind turbines can be used in ruralareas in developed countries where grid is not available [3]

The amplitude and frequency of generated voltage of windplants vary according to speed of wind [4] Hence powerelectronics interfaces are used to convert generated voltageto a fixed dc voltage which can later be either stored or con-verted into required ac voltage and frequencyGrid connectedwind energy conversion systems are more in trend In caseof grid faults WECS system connected to grid can be safelyislanded to serve critical loads connected to it

When a small wind turbine unit is connected to the gridthe voltage and frequency at the point of common couplingare controlled by the grid However in case of weak gridsvoltage sags anddisturbancesmay occurwhenWECS is inter-faced to grid In such situation the wind unit must support tothe grid voltage A wind energy conversion system can workin two different modes they are grid connected and stand-alone modes The stand-aloneislanding mode is a situationin which theWECS is isolated from the utility grid when griddisturbances due to network fault are cropped up Amonitor-ing unit is used to achieve it This unit will help in islandedoperation of WECS in a planned manner when voltage mag-nitude crosses the threshold value

Hindawi Publishing CorporationJournal of EnergyVolume 2015 Article ID 152898 12 pageshttpdxdoiorg1011552015152898

2 Journal of Energy

Voltage source converters


PMSGWind turbine

Filters Circuit breaker

GridCritical load

+

minus

AB

C

C

O

L1 L2

Vdc

Figure 1 Schematic diagram of WECS interfacing to grid

Authors in [5] verified experimentally the control algo-rithm applied in SWT working in both stand-alone andgrid connectedmodes Performance of synchronization algo-rithm is also checked which is used to connect DCAC con-verter back to grid after recovery from disturbance A novelmethod novel based on PLL is proposed by Teodorescu andBlaabjerg for grid failure detection and flexible mode switch-ing automatically in which the phase difference between thegrid and the inverter is used to determine grid failure andrecovered from fault [3] Jang andKimpresented three papersstarting in an algorithm improved successively which uti-lizes four system parameters voltage magnitude frequencyphase and total harmonic distortion (THD) of currentfor islanding detection The method monitors changes infour parameters and detects islanding by logical rules [6ndash8]During disturbances many system parameters change signif-icantly Hence selection of most vulnerable system parameterand selection of threshold value is very challenging task foreffective detection of disturbancesMany authors have imple-mented different methods based on wavelet transform (WT)for detection of power quality disturbance [9ndash14] Waveletenergy entropy variance standard deviation mean andwavelet energy are various statistical features suitable fordetection of power quality disturbances and an islandingevent

In this paper a WECS is developed using SIMULINKwith a flexible mode control strategy and synchronizationalgorithm to allow dual mode operation of it as and whenrequired A seamless transfer between the modes is realizedby opening and closing of the circuit breaker as shown inFigure 1 which disconnectsconnects the WECS fromto themain grid [15]Once theWECS is isolated from themain gridWECS will be responsible for maintaining the voltage andfrequencywhile supplying to load During autonomous oper-ation it is essential that inverters should not be overloadedSimultaneously system must ensure that the changes in loadare handled by inverters properly in a control manner

The DCAC converter of WECS is connected to grid toinject active and reactive power Mainly current-controlledvoltage source converter (VSC) is used in grid connectedmode [16 17] Conversely voltage controlled VSC is usedwhen the WECS works in the stand-alone mode To regulatevoltage andmaintain it constant is the major responsibility of

control method used in isolated mode ofWECS During griddisturbances the detection method based on wavelet energyfunction is used to change of mode of operation for gridconnected to isolatedmode ofWECS and vice versa A circuitbreaker is used for this and will switch between the modeson the basis of signal received from control method used

The main objective of this paper is to control the flexiblemode operation of control grid connected wind energyconversion systemusingwavelet energy based function Sincethe wind energy conversion system has been competent tooperate in both grid connected mode and stand-alone modeaccording to the grid conditions the control design is a bittricky This paper is presented as follows Section 2 describesthe inverter control in stand-alone mode of operation Thencontrol methods for grid connected operating mode includ-ing the PLL design and current regulation of the inverterare explained in Section 3 Use of wavelet energy functionfor detecting the status of grid is described in Section 4In Section 5 the verification of the control methods is donethrough simulation resultsThe control scheme implementedin WECS is tested using FPGA in Section 6 Finally conclu-sions are drawn in Section 7

2 Inverter Control in Stand-AloneMode of WECS

Electrical power available at the electrical generator outputof the wind energy conversion system is not sinusoidal innature To get the sinusoidal voltage at supply frequency andto keep the output power optimally constant power elec-tronic interfacing is done between generator and gridloadas shown in Figure 2 In general a power electronic interfacedevice is a combination of a rectifier an energy storage deviceto regulate the DC-link voltage and an inverter

Voltage source inverter of load side is responsible forproviding controlled output voltage in terms of frequency andamplitude [18 19] At load side inverter appropriate controlmethod is applied for generating switching pulses of inverterto produce output of required magnitude and frequency Toachieve it the controlmethod has an output voltage controllerusing any modulation technique Here space vector modula-tion method is implemented The schematic diagram of thecontrol method is shown in Figure 3

Journal of Energy 3

VSWT

Aerodynamic converter PMSG

Wind speed

Power electronic interface Ripple filter Nonlinear

load

Vgig

VdcVinv iinv Vsis VLiL

Trans lineimpedance

Figure 2 Power transfer stages in isolated WECS

3

2

1

1

1

Unit vector conversion Voltage regulatorDiscrete PWM

generator

Unit delayPULSE

Vsa

Vsb

Vsc

Usa

Usb

Usc

Vabc(pu)

m

1

ZUref pulsesVabc inv

Vd ref (pu)

Vref(pu)

Figure 3 Simulation block diagram for SVPWM to generate gate pulses

PI

PI

PI

PIcontrollers

PI

PI

Plowast

++

++

+

+minus

++minus minus

+minus

minus

+minus

+minus

Pmeasured

Vdc ref

Vdc measured

Qlowast

Qmeasured

Ilowastq

Id

Iq

Ilowastd

ed

eq

Vlowastd

Vlowastq

Va

Vb

Vc

SPW

M

DA

DB

DC

eminusj120579

120579

120596Lt

120596Lt

Figure 4 Grid side inverter control

In space vector PWM 3-phase sinusoidal modulatingsignal gets transformed into a revolving voltage vector witha constant magnitude and angular frequency Here the con-stant voltage magnitude is magnitude of desire voltage to beproduced and angular frequency is the sampling frequencyIn space vector based PWM instead of three modulatingsignals for 3-phase a revolving voltage vector is used as avoltage reference This voltage reference vector is sampledonce in every subcycle 119879

119904and sampled voltage vector gives

the voltage command for the given subcycle

3 Inverter Control of WECS in GridConnected Mode

Voltage oriented control (VOC) is mostly used for grid sidevoltage source inverter as shown in Figure 4 A phase locked

loop (PLL) is used to find out grid angle 120579 which is usedfor transformation of inverter output currents and outputvoltages in synchronous reference frame To obtain betterresponse of inverter it has been selected to decouple activeand reactive power The active power depends on the 119889-axis current component Similarly reactive power and 119902-axiscurrent component are directly related Therefore the 119889-axisPI controller controls active power and 119902-axis PI controllercontrols reactive power

Grid currents are converted in synchronous referenceframe currents 119894

119889 119894119902to provide separate control for active

and reactive power High power factor and sinusoidal gridcurrents can be obtained by doing so [20]

In order to operate under synchronization with gridthe system uses three PI controllers The DC-link voltagecontroller is used for calculating 119889-axis reference current to

4 Journal of Energy

PI controller

PLL controller

120596ff

Vlowastd = 0

Vq

Vd

1

s

+ ++minus

120596998400 120579998400

120579998400V120572 = 15Vmcos(120596t)V120573 = 15Vmsin(120596t)

abc minus 120572120573 120572120573 minus dqVbVa

Vc

Figure 5 Block diagram of phase locked loop based on synchronous reference frame

control active powerThe 119902-axis reference can be set to zero toget unity power factor By using PI controllers for controllingthe errors in 119889-axis and 119902-axis currents the control voltagesare generated for the 3-0 voltage source inverter in119875119876 controlmethod as shown in Figure 4 and are given by

119881lowast

119889= 119881119889+ 120596119871119905119894119902minus 119890119889

119881lowast

119902= 119881119902minus 120596119871119905119894119889minus 119890119902

(1)

where 119871119905is the total inductance on the grid side inverter and

119890119889and 119890119902are 119889-119902 components of grid side voltage vector

Tuning of PI controllers must be done accurately toobtain better control of DC-link voltage active power andreactive power The feedforward and cross coupling termsused in generation of reference voltage vector in synchronousreference frame help out in system linearization and makecontroller design easier The reference voltages 119881lowast

119889and 119881lowast

119902

are further transformed into and used to generate invertergate pulses through a SVPWM algorithm LCL filter is usedto improve the power quality at the inverter output

4 Grid Status Monitoring andTransition of Modes

41 Phase Locked Loop The utility grid status monitoringmust be done continuously in real time to ensure goodquality power supply to loads The grid status includes sens-ing fault overvoltage and undervoltage conditions Outagedetection is carried out in every sampling cycle by comparingthe instantaneous grid voltage The block diagram of thethree-phase PLL used for synchronization in the grid con-nected mode is as shown in Figure 5 A resonant filter can beadded tomake standardPLLmore robust in case of unbalanceand voltage harmonics

In case of grid failure islanded cannot be avoided Hencesuitable method must be used to detect grid failure For con-nected to grid again when grid returns to its normal condi-tion use of a synchronization algorithm is necessary prior totransition of mode from stand-alone to grid connected Theflowchart shown in Figure 6 is proposed for islanding detec-tion and further for transition from grid connected modeof WECS to stand-alone mode In case of grid disturbances

Grid disturbances detected

No

Yes

Remove previous window dataCaptured discretized signal in

memory

Perform DWT of each frame

Start

Selecting window length to form frame Set the value of threshold

coefficients

Perform mode transition fromgridconnected to stand-alone

Is energy lt threshold 1andenergy gt threshold 2

Calculation of wavelet energy of d6

Figure 6 Flowchart for detection of grid faultsislanding

mode change of WECS from grid connected to stand-aloneis performed in the following steps

(1) Identify grid condition using power quality monitor-ing

(2) Generate a signal to turn off circuit breaker in case ofgrid fault

Journal of Energy 5

Grid returns to normal condition

No

Yes


memory


coefficients

Start

Perform mode transition from

Selecting window length to form frame

Set the values of threshold

stand-alone to gridconnected

Is energy gt threshold 1andenergy lt threshold 2


Figure 7 Flowchart for returning to grid normal operation

(3) Mode transition can be done as soon as the circuitbreaker turns off Change the grid connected modeof WECS to stand-alone mode

(4) In case of stand-alone mode the control strategy willbe voltage controlled In voltage controlled mode ofload side inverter the reference value used for voltagewill be last value of grid voltage whenmode transitiontakes place

The flowchart shown in Figure 7 is proposed for detection ofgrid recovery and transition from stand-alone mode to gridconnected mode of WECS

42 Discrete Wavelet Transform Discrete wavelet transform(DWT) converts a time domain discretized signal into its cor-responding wavelet domain Principally the discrete wavelettransformation has two-phase determination of wavelet coef-ficients and calculation of detailed and approximated versionof the original signal in different scales of resolutions inthe time domain In filtering process the original signalis passed through two complementary filters and producesapproximate and detail coefficients To extend the frequencyresolution decomposition of signal is done repeatedly andsignal can be realized into two lower frequency ranges Thisprocess is known as multiresolution analysis (MRA) and goalof MRA is to represent a complex signal by several simplesignals to study them separately

43 Frame Length Coefficients of wavelet transform repre-sent the energy of the signalThese coefficients will be used tomeasure themagnitude of the disturbance in distorted signalIn real time application wavelet transform can be used as amonitoring tool when it becomes essential to detect distur-bances in minimum time For such cases distorted signal isprocessed through timewindowof fixed length frame Lengthof the frame means the number of sample points of discretedata signal for which wavelet energy has to be calculatedThe time window move forward along the signal and waveletenergy is calculated for each frame Frame length decides theresponse time of the method If length of the frame is longit will take more time in calculation and response time willget delayed Sampling frequency size of buffer and level ofdecomposition are three main factors which must be wiselyselected according to application A fixed frame length ofsample points 128 is used in this paper to obtain fast responsetime The sampling frequency selection has been doneaccording to Parsevalrsquos theorem and decomposition has beendone into 6th level

44Wavelet Energy Thediscrete wavelet divides a signal intoapproximated and detailed version of the original signal indifferent scales of resolutions in the time domain using low-pass and high-pass filters Decomposition of approximateversion can be repeated to obtain signal in required frequencysubbandswith number of approximate and detail coefficientsSum of coefficients square at a particular level represent theenergy of the signal at that level These coefficients will beused to compute the level of the disturbance in distortedsignal Wavelet energy measure based on wavelet analysis isable to observe the unsteady signal and complexity of thesystem at time-frequency planeThemother wavelet functionselected is db and scale factor 2 that is according to literaturereviews The signal is decomposed into 6th level Hence cD6coefficients will represent the fundamental frequency com-ponent of the signal and coefficients energy will be calculatedby using

119864119895=

119873

sum

119896=1

10038161003816100381610038161003816119863119895119896

10038161003816100381610038161003816

2

119895 = 1 2 119897 (2)

where 119863119895119896is the value of wavelet detail coefficients obtained

in decomposition from level 1 to level 119869119873 is the total numberof the coefficients at each decomposition level and 119864

119895is the

energy of the detail coefficients at decomposition level 119895

45 Deciding Threshold The most important part of moni-toring algorithm is deciding the setting for threshold levelThe value should be selected to change mode of WECSwhenever voltage of any phase crosses the standard limitssuch as voltage dip of less than 08 pu or voltage swell ofmagnitude more than 12 pu Simultaneously it should notcause unnecessary false tripping of circuit breaker in case ofsmall voltage dip or swell It is the value of wavelet energycalculated for output voltage signal (grid voltage) under nor-mal grid condition plus a variation allowed as per standardsFor calculating the threshold a reference signal of same frame

6 Journal of Energy



PMSGWind turbine

LCL filter

Voltagesensor

SVPWMSynchronous

reference framecontroller

Pulse isolationand amplifier

Critical loadCurrent

sensor

TransformerGrid

Circuit breaker

Voltagesensor

DWT controller

Voltagesensor

minus

+

S1

S2

S3

S4

S5

S6

O

AB

C

C

CDC

L1 L2

ig1 ig2ig3ig4 ig5ig6

Vlowastabc

VabcIabc

Figure 8 Schematic diagram of WECS connected to grid

Table 1 Parameters selection for proposed method

Parameter Peak voltage level (119881) Wavelet energy (1198812) Normalized wavelet energyPeak voltage of grid 325 23 lowast 119890610

5 23Permissible limit of voltage swell 390 40 lowast 119890610

5 40Permissible limit of voltage sag 260 11 lowast 119890610

5 11

length decomposed in 6th level using same mother waveletfunction db2 and coefficients energy of cD6 is calculatedPermissible variation in reference signal is considered andthe entire procedure is repeated to calculate lower and upperthreshold settings Table 1 is listing the wavelet energy fordifferent cases which helps in deciding lower and upperthreshold settings

5 Schematic Diagram of SystemResults and Discussions

A schematic diagram of grid connected WECS consists of3-0 PMSG full-bridge rectifier DC-link capacitor a 3-0IGBT based full-bridge inverter critical load LCL filtertransformer and circuit breaker and 400 volt 50Hz ac sourceis shown Figure 8 The system parameters used in simulationare given in Table 2 Simulation model of the system isdeveloped inMATLABsimulink environment All the valuesgiven in Table 2 have been calculated during mathematicalmodelling of WECS and grid connected WECS

51 Before Fault Figure 9 shows the output voltages undernormal grid condition It shows that the implemented controlmethod of voltage source inverter is maintaining the outputin desired form Figure 10 shows load voltage and loadcurrent under normal grid condition

52 During Fault It can be seen from Figure 11 that in caseof fault in phase B grid voltages of phase A and phase C have

Table 2 Design parameters for simulation

Description Symbolicrepresentation Value

Capacitor 119862dc 2200 120583FDC-link voltage 119881DC 650 voltsAC output voltage 119881

119904230 volts rms

AC output frequency 119891 50HzInverter side filter inductor 119871

102mH

Grid side filter inductor 1198712

01mHFilter capacitor 119862

110120583F

Inverter switching frequency 119891119904

3 kHz

been inceased Grid fault occurs at 119905 = 045 sec and continuestill 119905 = 07 sec Monitoring algorithm is constantly moni-toring the grid condition Such cases must be detected andreported to utility intactive inverter at the earliest so that sup-ply to critical load will be continued by intentional islandingof WECS The load is supplied fromWECS and grid currentis zero in case of grid fault Source current and load currents(local and shared load both) which are now supplied fromWECS in case of grid not present can be seen from Figure 12

Grid fault causes voltage variations in all the three phasesVoltage waveform of all the three phases and correspondingcoefficients energy plots are displayed in Figures 13 14 and 15respectively in red green (istead of yellow for improvedvisibility) and blue color for phase A phase B and phase CWavelet energy is normalized as calculated value has very

Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc

Figure 9 Three-phase grid voltages before fault

05 06 07 08 09 1

0

325400

Time (s)

Load voltageLoad current

Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400

Figure 10 Output waveform of load voltage and load current beforefault

large value and even a large change in coeficients energy can-not be clearly observed from actual plots of wavelet energyGrid voltages and corresponding coefficients energy plot aregraphical representation of change in wavelet coefficientsenergy in case of grid disturbances Threshold level withcalculated threshold further helps in transition of modesfrom grid connected to stand-alone and vice versa

At 119905 = 045 sec grid fault occurs wavelet based monitor-ing algorithm detects it at 048 sec and changes the mode ofWECS from grid connected to stand-alone Many distribu-tion systems use autoreclosing to clear temporary faults andhence it is essential to detect grid faults before the autore-closer operates to avoid out phase reclosing Grid fault causesvoltage variations in all the three phases which can beobserved clearly in Figure 16

Transition of mode from grid connected to stand-aloneoccured at 048 sec which is the total time taken by the pro-posed method in detection of grid disturbance and furtherisolate the WECS by operting circuit breaker which discon-nects it from grid When mode trasition occurs controllerof VSI changes its mode and continues to feed power to theload connected to it The grid monitoring algorithm detectsfault and changes mode of operation from grid connected

04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc

Figure 11 Three-phase grid voltages during disturbance

04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)

Source currentLocal load currentShared load current

Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30

Figure 12 Source current local load current and shared load cur-rent

mode to stand-alone mode at 048 sec when circuit breakersopensThe timings of mode change and circuit breaker status(1 means WECS grid connected 0 means disconnected fromgrid) can be seen from Figure 17 Figure 18 displays the lowerthreshold value due to which transition occurs

Grid voltage of all the phases and corresponding coef-ficients energy plots are shown in Figures 19 20 and 21respectively of phase A phase B and phase C Grid voltagesand corresponding coefficients energy plot are graphical rep-resentation of wavelet coefficients energy A small change involtages at load terminal (PCC) can be observed in the signaland associated wavelet energy plot in Figures 19 20 and 21that is due to change of load because of mode transitionWECS is now fed power to critical load and local loads con-nected to it Monitoring is still continued at PCC to check forgrid condition On the basis of threshold value of waveletenergy transition occurs from stand-alone mode to gridconnected mode which can be observed from Figures 19(a)and 19(b) at time 07 sec when fault is cleared

The power conditioning module for both the modesis based space vector pulse width modulation Instead ofconventional SVM triangular carrier based SVM is used to

8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)

Figure 13 (a) Voltage signal and (b) corresponding wavelet energy plot of phase A

03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)

Figure 14 (a) Voltage signal and (b) corresponding wavelet energy plot for fault in phase B

03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)

Figure 15 (a) Voltage signal and (b) corresponding wavelet energy plot of phase C

reduce computation burden as sector determination is notrequired in implementation The benefits of using DWT andwavelet energy based algorithm are accurate detection of startand end time of occurrence of any event or varaitions Accu-rate and quick detection can also be helpful for protection ofequipments as well as for the safety and stability of the system

6 Generation of Gate Pulses for Single PhaseBridge Inverter Using FPGA

In grid connected mode as well as in stand-alone mode ofWECS space vector pulse width modulation scheme hasbeen used for inverter control Its performance is checked

Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic

Figure 16 Three-phase voltages at PCC

03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es

Circuit breaker status (onoff)

Gridconnected mode of WECS

Stand-alone mode of WECS

X = 048Y = 0

Figure 17 Transition of modes

04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)

Wavelet energyLower threshold

Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)

Figure 18 Threshold settings

using FPGA with Altium NB 3000 Xilinx Spartan 3ANprocessor Step-by-step procedure for generating invertergate pulse is shown in Figure 22 XILINX ISE design suite145 is used formodel based design for PWMpulse generationfor single phase bridge inverter and Altium designer softwareis used for FPGA project design Number of steps has beenperformed for bit file generation using Altium design soft-ware It generates the programming file that is required for

downloading the design to the physical device A detailedprocedure for project design using FPGA is given in [21]

Schematic diagram to test SVPWM control method forgenerating gate pulses using FPGA is shown in Figure 23

Sine waveform and triangular carrier waveform of fre-quency 500Hz are given as input by ADC-SPI port andinverter gate pulses are obtained by user IO port which isshown in Figures 24 and 25 respectively

10 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)

Figure 19 (a) Voltage signal and (b) wavelet energy plot at PCC for phase A

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)

Figure 20 (a) Voltage signal and (b) wavelet energy plot at PCC for phase B

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)

Figure 21 (a) Voltage signal and (b) wavelet energy plot at PCC for phase C

7 Conclusions

The proposed method has been implemented for a 10 kWwind energy conversion system with rectifier-inverter inter-face which can work in grid connected mode as well as instand-alone mode The benefit of the used control schemeis that switching between the two operating modes happens

automatically on the basis of output of energy function Themost important feature of the system is its adaptability towork in both of the operatingmodes properly PLL is used forsynchronization in grid connected mode Simulation resultsdemonstrate the working and transition between the modesof WECS in only 3ms time and no transients appear duringtransition of modes

Journal of Energy 11

Bit file downloaded to FPGA board

Xilinx model based design using system generator

Netlist generation (VHDL file)

Altium designer software(VHDL file as a source file)

FPGA project design(open bus system design for SPI-ADC and

generated VHDL file as source file)

Compilation synthesis translate mappingplace and route time analysis and bit file generation

Figure 22 Step-by-step procedure for inverter gate pulse generationusing FPGA

IGBT module

Sine wave Triangular carrier

FPGA

S1 S2 S3 S4

LoadVDC

Figure 23 Schematic diagram for hardware setup

Figure 24 Load voltage and load current through RL load

Figure 25 Inverter output voltage and output gate pulses for singlephase bridge inverter

The tests concluded that detectionmethod has the follow-ing properties

(i) Detect grid disturbances event in just 3ms(ii) Accurate detection and quick transition maintain the

power quality and supply uninterrupted power tocritical load in case of grid outage

(iii) It is suitable for detection of steady state and transientstate disturbances both

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] R Teodorescu F Iov and F Blaabjerg ldquoFlexible developmentand test system for 11kW wind turbinerdquo in Proceedings of theIEEE 34th Annual Power Electronics Specialists Conference pp67ndash72 June 2003

[2] N A Orlando M Liserre R A Mastromauro and ADellrsquoAquila ldquoA survey of control issues in pmsg-based smallwind-turbine systemsrdquo IEEE Transactions on Industrial Infor-matics vol 9 no 3 pp 1211ndash1221 2013

[3] R Teodorescu and F Blaabjerg ldquoFlexible control of small windturbines with grid failure detection operating in stand-aloneand grid-connected moderdquo IEEE Transactions on Power Elec-tronics vol 19 no 5 pp 1323ndash1332 2004

[4] B Singh andG K Kasal ldquoSolid state voltage and frequency con-troller for a stand alone wind power generating systemrdquo IEEETransactions on Power Electronics vol 23 no 3 pp 1170ndash11772008

[5] A Milczarek and M Malinowski ldquoMonitoring and controlalgorithms applied to small wind turbine with grid-connectedstand-alonemode of operationrdquoPrzeglad Elektrotechniczny vol88 pp 18ndash22 2012

[6] S I Jang and K H Kim ldquoAn islanding detection methodfor distributed generations using voltage unbalance and totalharmonic distortion of currentrdquo IEEE Transactions on PowerDelivery vol 19 no 2 pp 745ndash752 2004

[7] S I Jang and K H Kim ldquoA new islanding detection algorithmfor distributed generations interconnected with utility net-worksrdquo in Proceedings of the 8th IEE International Conference


on Developments in Power System Protection vol 2 pp 571ndash574IET April 2004

[8] S-I Jang and K-H Kim ldquoDevelopment of a logical rule-based islanding detection method for distributed resourcesrdquoin Proceedings of the IEEE Power Engineering Society WinterMeeting vol 2 pp 800ndash806 January 2002

[9] J W Resende M L R Chaves and C Penna ldquoIdentificationof power quality disturbances using the MATLAB wavelettransform toolboxrdquo in Proceedings of the 4th InternationalConference on Power Systems Transients (IPST rsquo01) Rio deJaneiro Brazil June 2001

[10] C Kocaman and M Ozdemir ldquoComparison of statisticalmethods and wavelet energy coefficients for determining twocommon PQ disturbances sag and wellrdquo in Proceedings of the6th International Conference on Electrical and Electronics Engi-neering (ELECO rsquo09) pp I80ndashI84 November 2009

[11] P K Ray N Kishor and S R Mohanty ldquoIslanding and powerquality disturbance detection in grid-connected hybrid powersystem using wavelet and S-transformrdquo IEEE Transactions onSmart Grid vol 3 no 3 pp 1082ndash1094 2012

[12] R Tirumala N Mohan and C Henze ldquoSeamless transfer ofgrid-connected PWM inverters between utility-interactive andstand-alone modesrdquo in Proceedings of the 17th Annual IEEEApplied Power Electronics Conference and Expositions (APECrsquo02) pp 1081ndash1086 March 2002

[13] A Timbus M Liserre R Teodorescu P Rodriguez and FBlaabjerg ldquoEvaluation of current controllers for distributedpower generation systemsrdquo IEEE Transactions on Power Elec-tronics vol 24 no 3 pp 654ndash664 2009

[14] S W Mohod and V A Mohan ldquoPower quality issues and itrsquosmitigation technique in wind energy generationrdquo in Proceedingsof the 13th International Conference on Harmonics and Qualityof Power (ICHQP rsquo08) Wollongong Australia October 2008

[15] C N Bhende S Mishra and S G Malla ldquoPermanent magnetsynchronous generator-based standalone wind energy supplysystemrdquo IEEE Transactions on Sustainable Energy vol 2 no 4pp 361ndash373 2011

[16] J M Carrasco L G Franquelo J T Bialasiewicz et al ldquoPower-electronic systems for the grid integration of renewable energysources a surveyrdquo IEEE Transactions on Industrial Electronicsvol 53 no 4 pp 1002ndash1016 2006

[17] C L Anooja andN Leena ldquoSingle phase shunt active filter withfuzzy controller for harmonic mitigationrdquo International Journalof Scientific amp Engineering Research vol 4 no 9 pp 445ndash4512013

[18] L G B Rolim D R Da Costa Jr and M Aredes ldquoAnalysisand software implementation of a robust synchronizing PLLcircuit based on the pq theoryrdquo IEEE Transactions on IndustrialElectronics vol 53 no 6 pp 1919ndash1926 2006

[19] B Jain T Jain S Jain and R K Nema ldquoPower quality improve-ment of an isolated wind power generation systemrdquo IOSRJournal of Electrical and Electronics Engineering vol 9 no 3 pp33ndash50 2014

[20] K Zhou and D Wang ldquoRelationship between space-vectormodulation and three-phase carrier-based PWM a compre-hensive analysisrdquo IEEE Transactions on Industrial Electronicsvol 49 no 1 pp 186ndash196 2002

[21] X Computation ldquoGetting started with the Xilinx Virtex-6FPGAMI-605 evaluation Kitrdquo 2010

TribologyAdvances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

FuelsJournal of


Journal ofPetroleum Engineering


Industrial EngineeringJournal of


Power ElectronicsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

CombustionJournal of


Journal of


Renewable Energy

Submit your manuscripts athttpwwwhindawicom


StructuresJournal of


RotatingMachinery


EnergyJournal of


Hindawi Publishing Corporation httpwwwhindawicom

Journal ofEngineeringVolume 2014

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Nuclear InstallationsScience and Technology of


Solar EnergyJournal of


Wind EnergyJournal of


Nuclear EnergyInternational Journal of


High Energy PhysicsAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

2 Journal of Energy



PMSGWind turbine

Filters Circuit breaker

GridCritical load

+

minus

AB

C

C

O

L1 L2

Vdc

Figure 1 Schematic diagram of WECS interfacing to grid

Authors in [5] verified experimentally the control algo-rithm applied in SWT working in both stand-alone andgrid connectedmodes Performance of synchronization algo-rithm is also checked which is used to connect DCAC con-verter back to grid after recovery from disturbance A novelmethod novel based on PLL is proposed by Teodorescu andBlaabjerg for grid failure detection and flexible mode switch-ing automatically in which the phase difference between thegrid and the inverter is used to determine grid failure andrecovered from fault [3] Jang andKimpresented three papersstarting in an algorithm improved successively which uti-lizes four system parameters voltage magnitude frequencyphase and total harmonic distortion (THD) of currentfor islanding detection The method monitors changes infour parameters and detects islanding by logical rules [6ndash8]During disturbances many system parameters change signif-icantly Hence selection of most vulnerable system parameterand selection of threshold value is very challenging task foreffective detection of disturbancesMany authors have imple-mented different methods based on wavelet transform (WT)for detection of power quality disturbance [9ndash14] Waveletenergy entropy variance standard deviation mean andwavelet energy are various statistical features suitable fordetection of power quality disturbances and an islandingevent

In this paper a WECS is developed using SIMULINKwith a flexible mode control strategy and synchronizationalgorithm to allow dual mode operation of it as and whenrequired A seamless transfer between the modes is realizedby opening and closing of the circuit breaker as shown inFigure 1 which disconnectsconnects the WECS fromto themain grid [15]Once theWECS is isolated from themain gridWECS will be responsible for maintaining the voltage andfrequencywhile supplying to load During autonomous oper-ation it is essential that inverters should not be overloadedSimultaneously system must ensure that the changes in loadare handled by inverters properly in a control manner

The DCAC converter of WECS is connected to grid toinject active and reactive power Mainly current-controlledvoltage source converter (VSC) is used in grid connectedmode [16 17] Conversely voltage controlled VSC is usedwhen the WECS works in the stand-alone mode To regulatevoltage andmaintain it constant is the major responsibility of

control method used in isolated mode ofWECS During griddisturbances the detection method based on wavelet energyfunction is used to change of mode of operation for gridconnected to isolatedmode ofWECS and vice versa A circuitbreaker is used for this and will switch between the modeson the basis of signal received from control method used

The main objective of this paper is to control the flexiblemode operation of control grid connected wind energyconversion systemusingwavelet energy based function Sincethe wind energy conversion system has been competent tooperate in both grid connected mode and stand-alone modeaccording to the grid conditions the control design is a bittricky This paper is presented as follows Section 2 describesthe inverter control in stand-alone mode of operation Thencontrol methods for grid connected operating mode includ-ing the PLL design and current regulation of the inverterare explained in Section 3 Use of wavelet energy functionfor detecting the status of grid is described in Section 4In Section 5 the verification of the control methods is donethrough simulation resultsThe control scheme implementedin WECS is tested using FPGA in Section 6 Finally conclu-sions are drawn in Section 7

2 Inverter Control in Stand-AloneMode of WECS

Electrical power available at the electrical generator outputof the wind energy conversion system is not sinusoidal innature To get the sinusoidal voltage at supply frequency andto keep the output power optimally constant power elec-tronic interfacing is done between generator and gridloadas shown in Figure 2 In general a power electronic interfacedevice is a combination of a rectifier an energy storage deviceto regulate the DC-link voltage and an inverter

Voltage source inverter of load side is responsible forproviding controlled output voltage in terms of frequency andamplitude [18 19] At load side inverter appropriate controlmethod is applied for generating switching pulses of inverterto produce output of required magnitude and frequency Toachieve it the controlmethod has an output voltage controllerusing any modulation technique Here space vector modula-tion method is implemented The schematic diagram of thecontrol method is shown in Figure 3

Journal of Energy 3

VSWT


Wind speed


load

Vgig


Trans lineimpedance


3

2

1

1

1


generator

Unit delayPULSE

Vsa

Vsb

Vsc

Usa

Usb

Usc

Vabc(pu)

m

1


Vd ref (pu)

Vref(pu)


PI

PI

PI

PIcontrollers

PI

PI

Plowast

++

++

+

+minus

++minus minus

+minus

minus

+minus

+minus

Pmeasured

Vdc ref

Vdc measured

Qlowast

Qmeasured

Ilowastq

Id

Iq

Ilowastd

ed

eq

Vlowastd

Vlowastq

Va

Vb

Vc

SPW

M

DA

DB

DC

eminusj120579

120579

120596Lt

120596Lt












4 Journal of Energy

PI controller

PLL controller

120596ff

Vlowastd = 0

Vq

Vd

1

s

+ ++minus

120596998400 120579998400

120579998400V120572 = 15Vmcos(120596t)V120573 = 15Vmsin(120596t)


Vc



119881lowast

119889= 119881119889+ 120596119871119905119894119902minus 119890119889

119881lowast

119902= 119881119902minus 120596119871119905119894119889minus 119890119902

(1)





119902






No

Yes


memory


Start


coefficients








Journal of Energy 5


No

Yes


memory


coefficients

Start














119864119895=

119873

sum

119896=1

10038161003816100381610038161003816119863119895119896

10038161003816100381610038161003816

2

119895 = 1 2 119897 (2)



119895is the



6 Journal of Energy



PMSGWind turbine

LCL filter

Voltagesensor

SVPWMSynchronous




sensor

TransformerGrid

Circuit breaker

Voltagesensor

DWT controller

Voltagesensor

minus

+

S1

S2

S3

S4

S5

S6

O

AB

C

C

CDC

L1 L2


Vlowastabc

VabcIabc






5 11









119904230 volts rms


102mH



110120583F


3 kHz



Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc


05 06 07 08 09 1

0

325400

Time (s)


Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400





04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc


04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)


Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30





8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















Journal of Energy 3

VSWT


Wind speed


load

Vgig


Trans lineimpedance


3

2

1

1

1


generator

Unit delayPULSE

Vsa

Vsb

Vsc

Usa

Usb

Usc

Vabc(pu)

m

1


Vd ref (pu)

Vref(pu)


PI

PI

PI

PIcontrollers

PI

PI

Plowast

++

++

+

+minus

++minus minus

+minus

minus

+minus

+minus

Pmeasured

Vdc ref

Vdc measured

Qlowast

Qmeasured

Ilowastq

Id

Iq

Ilowastd

ed

eq

Vlowastd

Vlowastq

Va

Vb

Vc

SPW

M

DA

DB

DC

eminusj120579

120579

120596Lt

120596Lt












4 Journal of Energy

PI controller

PLL controller

120596ff

Vlowastd = 0

Vq

Vd

1

s

+ ++minus

120596998400 120579998400

120579998400V120572 = 15Vmcos(120596t)V120573 = 15Vmsin(120596t)


Vc



119881lowast

119889= 119881119889+ 120596119871119905119894119902minus 119890119889

119881lowast

119902= 119881119902minus 120596119871119905119894119889minus 119890119902

(1)





119902






No

Yes


memory


Start


coefficients








Journal of Energy 5


No

Yes


memory


coefficients

Start














119864119895=

119873

sum

119896=1

10038161003816100381610038161003816119863119895119896

10038161003816100381610038161003816

2

119895 = 1 2 119897 (2)



119895is the



6 Journal of Energy



PMSGWind turbine

LCL filter

Voltagesensor

SVPWMSynchronous




sensor

TransformerGrid

Circuit breaker

Voltagesensor

DWT controller

Voltagesensor

minus

+

S1

S2

S3

S4

S5

S6

O

AB

C

C

CDC

L1 L2


Vlowastabc

VabcIabc






5 11









119904230 volts rms


102mH



110120583F


3 kHz



Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc


05 06 07 08 09 1

0

325400

Time (s)


Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400





04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc


04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)


Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30





8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















4 Journal of Energy

PI controller

PLL controller

120596ff

Vlowastd = 0

Vq

Vd

1

s

+ ++minus

120596998400 120579998400

120579998400V120572 = 15Vmcos(120596t)V120573 = 15Vmsin(120596t)


Vc



119881lowast

119889= 119881119889+ 120596119871119905119894119902minus 119890119889

119881lowast

119902= 119881119902minus 120596119871119905119894119889minus 119890119902

(1)





119902






No

Yes


memory


Start


coefficients








Journal of Energy 5


No

Yes


memory


coefficients

Start














119864119895=

119873

sum

119896=1

10038161003816100381610038161003816119863119895119896

10038161003816100381610038161003816

2

119895 = 1 2 119897 (2)



119895is the



6 Journal of Energy



PMSGWind turbine

LCL filter

Voltagesensor

SVPWMSynchronous




sensor

TransformerGrid

Circuit breaker

Voltagesensor

DWT controller

Voltagesensor

minus

+

S1

S2

S3

S4

S5

S6

O

AB

C

C

CDC

L1 L2


Vlowastabc

VabcIabc






5 11









119904230 volts rms


102mH



110120583F


3 kHz



Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc


05 06 07 08 09 1

0

325400

Time (s)


Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400





04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc


04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)


Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30





8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















Journal of Energy 5


No

Yes


memory


coefficients

Start














119864119895=

119873

sum

119896=1

10038161003816100381610038161003816119863119895119896

10038161003816100381610038161003816

2

119895 = 1 2 119897 (2)



119895is the



6 Journal of Energy



PMSGWind turbine

LCL filter

Voltagesensor

SVPWMSynchronous




sensor

TransformerGrid

Circuit breaker

Voltagesensor

DWT controller

Voltagesensor

minus

+

S1

S2

S3

S4

S5

S6

O

AB

C

C

CDC

L1 L2


Vlowastabc

VabcIabc






5 11









119904230 volts rms


102mH



110120583F


3 kHz



Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc


05 06 07 08 09 1

0

325400

Time (s)


Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400





04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc


04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)


Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30





8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















6 Journal of Energy



PMSGWind turbine

LCL filter

Voltagesensor

SVPWMSynchronous




sensor

TransformerGrid

Circuit breaker

Voltagesensor

DWT controller

Voltagesensor

minus

+

S1

S2

S3

S4

S5

S6

O

AB

C

C

CDC

L1 L2


Vlowastabc

VabcIabc






5 11









119904230 volts rms


102mH



110120583F


3 kHz



Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc


05 06 07 08 09 1

0

325400

Time (s)


Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400





04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc


04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)


Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30





8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















Journal of Energy 7

05 055 06 065 07 075 08

0100200300400

Time (s)

Grid

vol

tage

s (V

)

minus100

minus200

minus300

minus400

VaVbVc


05 06 07 08 09 1

0

325400

Time (s)


Load

vol

tage

(V)

Load

curr

ent (

amps

)

minus200

minus325minus400





04 045 05 055 06 065 07 075 08 085 09

325

0

325

500

Time (s)

Grid

vol

tage

s (V

)

minus500

VaVbVc


04 045 05 055 06 065 07 075 08 085 09

0

10

20

30

Time (s)


Sour

ce cu

rren

t (am

ps)

minus10

minus20

minus30





8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















8 Journal of Energy

03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Grid

vol

tage

pha

se A

(V)

minus325

minus500

Vga

(a)

03 04 05 06 07 08 09 1 110

102030405060708090

100

Time (s)

Wav

elet e

nerg

y ph

ase A

(V2)

EVa

(b)


03 04 05 06 07 08 09 1 11500

0

325

500

Time (s)

Grid

vol

tage

pha

se B

(V)

minus325

Vgb

(a)

03 04 05 06 07 08 09 1 110

5

10

15

20

25

Time (s)

Wav

elet e

nerg

y ph

ase B

(V2)

EVb

(b)


03 04 05 06 07 08 09 1 11

325

0

325

500

Time (s)

Grid

vol

tage

pha

se C

(V)

minus500

Vgc

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y ph

ase C

(V2)

EVc

(b)





Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















Journal of Energy 9

04 045 05 055 06 065 07 075 08 085 09

0100200300400

Time (s)In

vert

er v

olta

ges (

V)

minus100

minus200

minus300

minus400

ViaVibVic


03 04 05 06 07 08 09 1 110

02040608

112141618

2

Time (s)

Tran

sitio

n of

mod

es




X = 048Y = 0


04 045 05 055 06 065 07 075 08 085 0905

10152025303540

Time (s)


Lower threshold

Wav

elet e

nerg

y ph

ase A

(V2)







03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


















03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se A

(V)

minus325

minus500

Via

(a)

03 04 05 06 07 08 09 1 112021222324252627282930

Time (s)

Wav

elet e

nerg

y PC

C ph

ase A

(V2)

X = 045009Y = 242683

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se B

(V)

minus325

minus500

Vib

(a)

03 04 05 06 07 08 09 1 1110

15

20

25

30

35

40

Time (s)

Wav

elet e

nerg

y PC

C ph

ase B

(V2)

EVa at PCC

(b)


03 04 05 06 07 08 09 1 11

0

325

500

Time (s)

Volta

ge at

PCC

pha

se C

(V)

minus325

minus500

Vic

(a)

03 04 05 06 07 08 09 1 1110

20

30

Time (s)

Wav

elet e

nerg

y PC

C ph

ase C

(V2)

EVc at PCC

(b)


7 Conclusions












IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of


























IGBT module


FPGA

S1 S2 S3 S4

LoadVDC










References




























FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of





































FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of





















FuelsJournal of







Advances in



Journal of


Renewable Energy





RotatingMachinery


EnergyJournal of

















Documents

Research Article Flexible Mode Control of Grid Connected ...downloads.hindawi.com/journals/jen/2015/152898.pdf · controls reactive power. Grid currents are converted in synchronous