Simulation Analysis of 100kw Integrated Segmented Energy Storage for Grid Connected Pv System

8/11/2019 Simulation Analysis of 100kw Integrated Segmented Energy Storage for Grid Connected Pv System

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International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976

6545(Print), ISSN 0976 6553(Online) Volume 3, Issue 2, July- September (2012), IAEME

SIMULATION ANALYSIS OF 100KW INTEGRATED SEGMENTED

ENERGY STORAGE FOR GRID CONNECTED PV SYSTEM

M.Sujith(1)

, R.Mohan(2)

, P.Sundravadivel(3)

(1)Assistant professor, Vidyaa Vikas College of Engineering and

Technology,Tiruchengode-637214 Email ID: [email protected]

(2)Assistant professor, Vidyaa Vikas College of Engineering and

Technology,Tiruchengode-637214 Email ID: [email protected](3)

Assistant professor, K.S.R. College of Engineering,Tiruchengode-637214

Email ID: [email protected]

ABSTRACT

The present a single-phase photovoltaic (PV) system integrating segmented

energy storage (SES) using cascaded multilevel inverter. The system is designed to

coordinate power allocation among PV, SES, and utility grid, mitigate the overvoltage at

the Point of common point (PCC), and achieve wide range reactive power compensation.

The power allocation principle between PV and SES is described by a vector diagram.An appropriate reactive power allocation coefficient (RPAC) is designed to avoid duty

cycle saturation and over modulation so that wide range reactive power compensation

and good power quality can be achieved simultaneously. The self-regulating power

allocation control system integrating the preferred RPAC and an advanced active power

control algorithm are developed to achieve the aforesaid objective. Simulation results are

provided to demonstrate the effectiveness of the proposed cascaded PV system

integrating SES.

Key Words : Photovolatic, Segmented Energy Storage, Reactive power Allocation

Coefficient, Point of common Point

I INTRODUCTION

Energy Storage (ES) elements such as batteries ES have been applied to grid-

connected residential PV systems for peak power shavings and backup power. Recently,

it is being looked at as a possible solution for improvement of the power quality of the

grid. Research in proves that integration of small energy storage can effectively reduce

the overvoltage caused by reverse power flow. Moreover, battery-integrated PV systems

can improve grid quality by introducing reactive power compensation and harmonics

cancellation.

INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &

TECHNOLOGY (IJEET)

ISSN 0976 6545(Print)

ISSN 0976 6553(Online)

Volume 3, Issue 2, July September (2012), pp. 164-173

IAEME: www.iaeme.com/ijeet.html

Journal Impact Factor (2012): 3.2031 (Calculated by GISI)

www.jifactor.com

IJEET

I A E M E


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International Journal of Ele

6545(Print), ISSN 0976 6553

Traditionally, two ki

integrated PV systems: ac-l

separate dc/ac converters for

dc/ac converter for the PV a

advantages, they both require

the battery and the grid. Hoconditioning system with ES

Another disadvantage is that

converters in order to achieve

II PV-GRID CONNECTE

The configuration of

Fig.1. It consists of solar PV

output filter and grid voltage

parallel configuration to mat

current (DC) link capacitor m

voltage source inverter. Theinput voltage into AC sinusoi

the filter output pass through

voltage to 220 VRMS requi

consists of a battery bank forgrid failure.

Photovoltaic power s

and operational requirements,

connected to other power so

are grid-connected or utility-i

Fig.1 S

(a)CIRCUIT OPERATION

The PV module is co

devices are integrated throug

in stand-alone and grid-conne

the cascaded multilevel inv

trical Engineering and Technology (IJEET),

Online) Volume 3, Issue 2, July- September (201

ds of system configurations have been used

ink system and dc-link system. The ac-link

he PV array and battery. The dc-link system ha

rray and battery. Although each configuration

two conversion stages, i.e., dc/dc and dc/ac st

wever, it is reported that the efficiency of cis 8% lower than the traditional PV system

high switching frequency must be implemente

lower voltage total harmonic distortion (THD).

SYSTEM

a single phase grid connected PV system is i

array, input capacitor, single phase inverter, a

source. The solar PV modules are connected

h the required solar voltage and power ratin

aintains the solar PV array voltage at a certain

ingle phase inverter with the output filter conal voltage by means of appropriate switch sign

an isolation step up transformer to setup the

red by the electric utility grid and load. The

supplying the electrical loads of the clinic in ca

stems are generally classified according to the

their component configurations, and how the

rces and electrical loads. The two principal cl

teractive systems and stand-alone systems.

hematic Diagram of PV-Grid System

nnected to the grid through an H-bridge inve

cascaded H-bridge cells. The proposed system

cted mode through a static transfer switch (ST

rter is usually adopted for high-power and

ISSN 0976

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in battery-

system has

s a common

has its own

ge, between

rrent powerwithout ES.

d for all the

llustrated in

nd low pass

in a series-

. The direct

level for the

erts the DCals and then

filter output

system also

e of electric

ir functional

quipment is

assifications

ter. The ES

can operate

). Although

high-voltage


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applications, this research revealed the following advantages of applying this topology.

First, the cascaded multilevel converter with separate dc source is ideal for connecting

PV and SES. The SES can be controlled and maintained individually which improves the

system reliability. Second, this topology integrates ES charge/discharge control and dc/ac

power conversion. Therefore, there is only one conversion stage from ES to grid, which

leads to higher efficiency, lower cost, and lighter weight. Third, the wide range reactivepower compensation and proper active power allocation can be achieved simultaneously

to improve power quality.

In the proposed topology, the power allocation strategy between PV and SES

plays the key role since the power allocation and output voltage generation are coupled

with each other. An RPAC is then selected by plot analysis under different conditions.

The self-regulating power allocation control system is developed to achieve active power

control between PV and SES, and wide range reactive power compensation.

(b)Battery Active Power Control Algorithm

The battery active power control algorithm includes battery active power

reference generation and active power control. Depending on the system operation

conditions, the active power dispatch among PV, load, grid, and batteries may come intofive operation states as follows.

Operation state 1:if P_main0.2,no power will be delivered to

grid. Batteries will provide power to meet the load requirement. Each battery is

controlled to provide half of (P_loadP_main) power.

Operation state 2: if P_mainP_load, Vpcc>Vpcc limit and SOC P_load, Vpcc>Vpcc limit, but SOC >0.9, the MPPT

for PV module cannot be achieved. P_main is limited to the upper power limit

P_main_limit. P_grid is limited to the upper power limitP_grid_limit. Batteries are not

allowed to absorb power.

(c)

Power Allocation Analysis

The flexible active and reactive power allocation among PV, SES (ES1 and ES2),

and utility grid. In this paper, a battery is used as SES. Due to the PV power variation

under different operation conditions, SES will be charged or discharged to meet the

load/grid requirement so as to improve power quality and maintain system stability. Inaddition, the low-order harmonic voltages being included in the quasi-square-wave of the

main inverter output voltage can be cancelled by the equivalent negative harmonic

voltage generated from auxiliary inverters. The proposed PV system with SES is able to

operate in both stand-alone mode and grid-connected mode through an STS.


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6545(Print), ISSN 0976 6553

III SIMULATION ANALYSIIt is a detailed model o

converter and a three-phase threTracking (MPPT) is implemente

Incremental Conductance + IntThe detailed model contains:

PV array delivering a m 5-kHz boost converter (

DC at maximum power

controller that uses the

1980-Hz (33*60) 3-leve260 V AC and keeps uni

10-kvar capacitor bank

100-kVA 260V/25kV th

Utility grid model (25-k

In the average model the b

sources generating the AC voltmodel does not represent harmo

system interaction is preserved.resulting in a much faster simula

Note that in the average mo

loops are required to get an itertimes are used. These algebraic l

(a) PV ArrayThe 100-kW PV array of the de

consists of 66 strings of 5 serieskW). Open the PV-array block

for one module are:

Number of series-connected cellOpen-circuit voltage: Voc= 64.2Short-circuit current: Isc = 5.96

Voltage and current at maximuThe PV array block menu allow

module and for the whole arreproduced below.



a 100-kW array connected to a 25-kV grid via a

-level Voltage Source Converter (VSC). Maximud in the boost converter by means of a Simulink m

gral Regulator technique.

ximum of 100 kW at 1000 W/m2 sun irradiance.range blocks) increasing voltage from PV natural v

to 500 V DC. Switching duty cycle is optimized

Incremental Conductance + Integral Regulator tec

l 3-phase VSC (blue blocks). The VSC converts thety power factor.

iltering harmonics produced by VSC.

ree-phase coupling transformer.

distribution feeder + 120 kV equivalent transmissi

ost and VSC converters are represented by equi

ge averaged over one cycle of the switching freqnics, but the dynamics resulting from control syste

This model allows using much larger time steps (5tion.

el the two PV-array models contain an algebraic lo

tive and accurate solution of the PV models whenoops are easily solved by Simulink.

tailed model uses 330 Sun Power modules (SPR-3

connected modules connected in parallel (66*5*30enu and look at model parameters. Manufacturer

s : 96V

power: Vmp =54.7 V, Imp= 5.58 Ayou to plot the I-V and P-V characteristics for one

ray. The characteristics of the SunPower-SPR3

ISSN 0976

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C-DC boost

Power Pointdel using the

ltage (272 V

by the MPPT

nique.

500 V DC to

on systems).

alent voltage

ency. Such am and power

0 microsecs),

op. Algebraic

large sample

5). The array

.2 W= 100.7specifications

5 array are


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6545(Print), ISSN 0976 6553

Fig.2 I-

Red dots on blue curves ind

Imp) under standard test cond

(b)

Boost converterIn the detailed model,

273.5 V to 500V. This conv

duty cycle in order to generat

Look under the mask of thealgorithm is implemented. Fo

paper:

Moacyr A. G. de Brit

Carlos A. Canesin Compara

2011 International Conferenc

(c)VSC converter

The three-level VSCunity power factor. The cont

which regulates DC link volta

Id and Iq grid currents (active

Id current reference is

reference is set to zero in o

outputs of the current controll

by the PWM three-level pulse

The control system

controllers as well as for th

generators of Boost and VSC

appropriate resolution of PW

1. Run the photo.mdl for 3

Scopes.

From t=0 sec to t= 0.

voltage corresponds t

trace on Scope Boost)

link capacitors are cha



V and P-V characteristics of PV array

icate module manufacturer specifications (Vo

itions (25 degrees Celsius, 1000 W/m2).

the boost converter (orange blocks) boosts DC

erter uses a MPPT system which automaticall

the required voltage to extract maximum pow

Boost Converter Control block to see hor details on various MPPT techniques, refer to t

, Leonardo P. Sampaio, Luigi G. Jr., Guilherm

tive Analysis of MPPT Techniques for PV A

on Clean Electrical Power (ICCEP).

blue blocks) regulates DC bus voltage at 500ol system uses two control loops: an external

ge to +/- 250 V and an internal control loop wh

and reactive current components).

the output of the DC voltage external controll

rder to maintain unity power factor. Vd and

er are converted to three modulating signals U

generator.

ses a sample time of 100 ms for voltage

PLL synchronization unit. In the detailed

converters use a fast sample time of 1ms in or

waveforms.

econds and observe the following sequence

5 sec, pulses to Boost and VSC converters are

o open-circuit voltage (Nser*Voc=5*64.2=32

. The three-level bridge operates as a diode rect

rged above 500 V (see Vdc_meas trace on Sco

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, Isc, Vmp,

oltage from

y varies the

r.

the MPPTe following

A. e Melo,

plications,

and keepscontrol loop

ch regulates

r. Iq current

Vq voltage

ef_abc used

and current

odel, pulse

er to get an

f events on

blocked. PV

1 V, see V

ifier and DC

e VSC).


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6545(Print), ISSN 0976 6553

At t=0.05 sec, Boost

regulated at Vdc=500

on Scope Boost) and

at t=0.25 sec. Resul

0.5)*500=250 V (see

kW (see Pmean traceW/m2 irradiance is 1

current at 25 kV bus a

At t=0.4 sec MPPT is

by varying duty cycle

(100.7 kW) is obtaine

voltage =274 V as exp

273.5 V).

From t=0.7 sec to t=1.

250 W/m2. MPPT con

irradiance has decreas

voltage and power are

continues tracking ma From t=1.5 sec to 3 se

illustrate the good per

Fig. 3 Simulation



and VSC converters are de-blocked. DC lin

. Duty cycle of boost converter is fixed (D=

un irradiance is set to 1000 W/m2. Steady sta

ting PV voltage is therefore V_PV = (1-D

V trace on Scope Boost). The PV array output

on Scope Boost) whereas maximum power0.7 kW. Observe on Scope Grid that phase a

re in phase (unity power factor).

nabled. The MPPT regulator starts regulating

in order to extract maximum power. Maximum

when duty cycle is D=0.453. At t=0.6 sec, PV

ected from PV module specifications (Nser*V

2 sec, sun irradiance is ramped down from 100

tinues tracking maximum power. At t=1.2 sec

d to 250 W/m2, duty cycle is D=0.485. Corres

Vmean= 255 V and Pmean=22.6 kW. Note tha

imum power during this fast irradiance change various irradiance changes are applied in orde

ormance of the MPPT controller.

Diagram for 100KW Grid Connected PV Arra

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k voltage is

.5 as shown

e is reached

)*Vdc= (1-

power is 96

ith a 1000voltage and

V voltage

power

mean

p=5*54.7=

W/m2 to

hen

onding PV

the MMPT

.r to


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Fig.4. Waveforms of Boost Converter

Fig.5. Waveform for Modulation Index and Inverter


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Fig.6. Response of Voltage Source Converter

Fig.7. Synchronized Grid Power


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Fig. 8. Grid Voltage and Current

IV CONCLUSION

This paper has addressed the development of the cascaded PV system integrating

SES. The proposed PV system can provide enhanced active power smoothing and

expanded reactive power compensation. A developed dual-stage DFT PLL method was

verified to be able to achieve the active and reactive power separation and improve the

dynamic performance of the PV system. A coordinated power allocation strategy based

on the proposed dual-stage DFT PLL can effectively allocate the active and reactive

power between PV and SES. An appropriate reactive power allocation coefficient k2 was

derived from RPAC analysis under different conditions to achieve wide range reactive

power compensation without degrading power quality. The particular battery active

power control algorithm was conducted to deduce the active power allocation coefficient

k1 and improve the system stability and reliability. Overvoltage of PCC caused by

reverse power flow is eliminated by appropriately dispatching PV power to SES. The

simulation results confirmed the validity of the proposed power allocation control.

V REFERENCES

1.

Dr P.S. Bimbhra (2012) Power Electronics, Khanna publishers, Fourth edition,

pp.127-198.

2. Moacyr A. G. de Brito, Leonardo P. Sampaio, Luigi G. Jr., Guilherme A. e Melo,

Carlos A. Canesin Comparative Analysis of MPPT Techniques for PV

Applications, 2011 International Conference on Clean Electrical Power (ICCEP).

3. Gopal k. Dubey (2007) Fundamentals of Electric Drives, Narosa publishing

house, Second edition, pp.385-397.


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Simulation Analysis of 100kw Integrated Segmented Energy Storage for Grid Connected Pv System