Improved Performance Of Diesel Driven Permanent Magnet

Synchronous Generator Using Battery Energy Storage System

ByJANE MARIA S

Edited BySarath S Nair

www.technologyfuturae.com

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OVERVIEW

Introduction Need of BESS Schematic block of BESS based supply system Control scheme of BESS-PMSG system Principle of operation & control Modeling of Control Scheme Advantages Summary

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INTRODUCTION

• BESS (Battery Energy storage System) is used for load compensation of PMSG driven by diesel engine to enhance its performance.

• BESS has capabilities of reactive power, harmonics, unbalanced load compensation.

• Control of BESS is achieved by indirect current control scheme.

• The voltage at PCC is controlled using BESS under various loads.

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NEED OF BESS

• Diesel engine based electricity generation unit (DG set) may be loaded with unbalanced & non-linear loads.

• Unbalanced & distorted currents lead to unbalanced & distorted 3 phase voltages at PCC.

• It leads to increased fuel consumption, poor efficiency & reduced life of DG sets.

• It leads to operation of DG sets under derated condition, results into increased cost of the system.

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contd..

• The BESS system may improve the performance of DG set to feed unbalanced load without derating.

• BESS can provide compensation of harmonics & reactive power & load balancing.

• PMSG are most efficient machines & robust due to brushless construction.

• Integration of BESS with such a DG set provides active power conditioning .

• BESS can absorb excessive power when load is less & can replenish at the time of peak load. 5

Schematic Diagram for BESS based Supply system

BESS-PMSG based DG set feeding to variety of loads:

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SYSTEM DESCRIPTION

• Consists of the IGBT based 3-phase 3-leg VSI system.

• BESS regulates the PCC voltage constant. Hence, voltage regulator is avoided.

• The governor block is disabled since the active power drawn from PMSG is kept constant.• This leads to single point of operation & load leveling

with BESS.

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contd..

• PMSG is operated at constant rated power with proper utilization of generated electrical energy.

• The surplus power is absorbed by the BESS and during peak load,it replenishes the increased requirement of load, which offers load leveling.

• Here, active component of source current remains fixed, whereas reactive power component depends upon requirement of AC terminal voltage control.

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Control Scheme of BESS-PMSG system

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Principle of Operation & Control

• 3 phase ism* have two components:• The in-phase component• The quadrature component -(w. r. to phase voltages)

• The in phase components of ref. source currents (isad*, isbd*, iscd*) is required to charge battery of BESS and (or) to feed active power to the load.

• This active power component may be kept constant.• The magnitudes of ismd* can be assigned to a constant

value.10

MODELING of Control Scheme

• Mainly used to derive ism*,which are used in PWM current controller.

• The two components of ism* are estimated as follows:• The in-phase unit vectors,

ua = va / Vm;

ub = vb / Vm;

uc=vc/Vm

Vm = 2/3 √(va2+vb

2+vc2)

va, vb, and vc are the instantaneous voltages at PCC

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Contd..

• va = vsan - Rs isa - Ls pisa

vb = vsbn - Rs isb - Ls pisb

vc = vscn - Rs isc - Ls pisc vsan, vsbn, and vscn are the three phase instantaneous input

supply voltages at PCC

• vsan=vsm sin(ωt)

vsbn=vsm sin(ωt-2π/3)

vscn=vsm sin(ωt+2π/3)

• The in-quadrature unit vectors can be derived by taking a quadrature transformation of the in-phase unit vectors ua, ub and uc as:

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Contd..

• wa = - ub/ √3 + uc/ √3

wb = √3 ua/ 2 + (ub -uc)/(2 √3)

wa = -√3 ua/ 2 + (ub -uc)/(2 √3)

• The quadrature component of the reference source currents is computed as:

• Ver(n) = Vref(n) – Vm(n)

• I*smq(n) = I*smq(n-1) +K p { Ver(n) - Ver(n-1) }+ KiVer(n)

• i*saq = I*smq wa;

i*sbq = I*smq wb;

I*scq = I*smq wc

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Contd..

• The in-phase component of the reference source currents is computed as:

i*sad = I*smd ua;

i*sbd = I*smd ub;

i*scd = I*smd uc

• Reference source currents are computed as:• i*sa=i*saq+i*sad;

i*sb= i*sbq + i*sbd;

i*sc= i*scq + i*scd 14

Modeling of Permanent Magnet Synchronous Machine

• Vd =Rsid+p φ d-wr φ q

• Vq = Rsiq + p φ q + wr φ d

• V’fd = R’fdi’fd + p φ’fd

• V’kd = R’kdi’kd + p φ’kd

• V’kq1=R’kq1i’kq1+p φ’kq1

• V’kq2 = R’kq2i’kq2 + p φ’kq2

where,

• φ d = Ld id + Lmd ( i’fd + i’kd)

• φ q = Lq iq + Lmq i’kq

• φ’fd = L’fd i’fd + Lmd ( id + i’kd)

• φ’kd = L’kd i’kd + Lmd ( id + i’fd)

• φ’kq2= L’kq2i’kq2+Lmqiq 15

Modeling of System Loads

1. Balanced and Unbalanced Delta Connected Linear Loads The current derivative model equations are given as:

p iLap = (vab - RL iLap )/ LL

p iLbp = (vbc - RL iLbp )/ LL

p iLcp = (vca - RL iLcp )/ LL

In case of unbalanced loads the particular phase of the load is made open.

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Contd..

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2. Non-Linear Load The basic equations in derivative form are as:

p id = (vmax-vd )/ 2 Ls

p vd = (id- io)/ Co

Contd..3. The Motor Load

• The model equations defining transient performance of an induction machine are represented as:

[v] = [R] [i] +[L] p[i] + wr [G] [i]

Te = J(2/poles) p wr + TL

where [ v ] = [vsd vsq vrd vrq ]T

[ i ] = [isd isq ird irq ]T

Te = (3/4) poles Lm (isq ird – isd irq)

• p[i] = [L]-1 {[v] – [R] [i] – wr [G] [i]}

pwr = poles (Te – TL) / (2 J)

For generating mode load torque is made negative.18

Advantages of BESS-PMSG system

• The system can feed unbalanced loads without derating.

• Can provide compensation for harmonics and reactive power and load balancing.

• It provides active power conditioning featuring power quality improvement.

• It avoids the need of voltage regulators.• It offers load leveling.

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SUMMARY

• The BESS can be used to improve the performance of a diesel driven PMSG. It regulates supply currents under unbalanced load currents.

• The control scheme & modeling of BESS-PMSG system is discussed.

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REFERENCES

[1] Jashvir Singh, Rajveer Mittal, D. K. Jain, ”Improved Performance of Diesel Driven Permanent Magnet Synchronous Generator Using Battery Energy Storage System”, IEEE Electrical Power & Energy Conference 2009

[2] M.D. Anderson, D. S. Carr, ”Battery Storage Technologies”,Voltage.81,No.3,pp 475-479, March 1993

[3]www.wikipedia.org

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