1. Improved Performance Of Diesel Driven Permanent Magnet Synchronous Generator Using Battery Energy Storage System By JANE MARIA S Edited By Sarath S Nair www.technologyfuturae.com 1

2. 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 2

3. 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. 3

4. 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. 4

5. 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

6. Schematic Diagram for BESS based Supply system BESS-PMSG based DG set feeding to variety of loads: 6

7. 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. 7

8. 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. 8

9. Control Scheme of BESS-PMSG system 1111 12 13 14121314 9

10. Principle of Operation & Control 3 phase i sm * have two components: The in-phase component The quadrature component -(w. r. to phase voltages) The in phase components of ref. source currents (i sad *, i sbd *, i scd *) 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 i smd * can be assigned to a constant value. 10

11. MODELING of Control Scheme Mainly used to derive i sm *,which are used in PWM current controller. The two components of i sm * are estimated as follows: The in-phase unit vectors, u a = v a / V m ; u b = v b / V m ; u c =v c /V m Vm = 2/3 √(v a 2 +v b 2 +v c 2 ) v a, v b, and v c are the instantaneous voltages at PCC 11

12. Contd.. v a = v san - R s i sa - L s pi sa v b = v sbn - R s i sb - L s pi sb v c = v scn - Rs i sc - L s pi sc v san, v sbn, and v scn are the three phase instantaneous input supply voltages at PCC v san =v sm sin(ωt) v sbn =v sm sin(ωt-2π/3) v scn =v sm sin(ωt+2π/3) The in-quadrature unit vectors can be derived by taking a quadrature transformation of the in-phase unit vectors u a, u b and u c as: 12

13. Contd.. w a = - u b / √3 + u c / √3 w b = √3 u a / 2 + (u b -u c )/(2 √3) w a = -√3 u a / 2 + (u b -u c )/(2 √3) The quadrature component of the reference source currents is computed as: V er(n) = V ref(n) – V m(n) I* smq (n) = I* smq(n-1) +K p { Ver(n) - V er(n-1) }+ KiV er(n) i* saq = I* smq w a ; i* sbq = I* smq w b ; I* scq = I* smq w c 13

14. Contd.. The in-phase component of the reference source currents is computed as: i* sad = I* smd u a ; i* sbd = I* smd u b ; i* scd = I* smd u c 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

15. Modeling of Permanent Magnet Synchronous Machine V d =R s i d +p φ d -w r φ q Vq = R s i q + p φ q + w r φ d V’ fd = R’ fd i’ fd + p φ’ fd V’ kd = R’ kd i’ kd + p φ’ kd V’ kq1 =R’ kq1 i’ kq1 +p φ’ kq1 V’ kq2 = R’ kq2 i’ kq2 + p φ’ kq2 where, φ d = L d i d + L md ( i’ fd + i’ kd ) φ q = L q i q + L mq i’ kq φ’ fd = L’ fd i’ fd + L md ( i d + i’ kd ) φ’ kd = L’ kd i’ kd + L md ( i d + i’ fd ) φ’ kq2 = L’ kq2 i’ kq2 +L mq i q 15

16. Modeling of System Loads 1.Balanced and Unbalanced Delta Connected Linear Loads The current derivative model equations are given as: p i Lap = (v ab - R L i Lap )/ L L p i Lbp = (v bc - R L i Lbp )/ L L p i Lcp = (v ca - R L i Lcp )/ L L In case of unbalanced loads the particular phase of the load is made open. 16

17. Contd.. 17 2. Non-Linear Load The basic equations in derivative form are as: p i d = (v max -v d )/ 2 Ls p v d = (i d - i o )/ C o

18. Contd.. 3. The Motor Load The model equations defining transient performance of an induction machine are represented as: [v] = [R] [i] +[L] p[i] + w r [G] [i] Te = J(2/poles) p w r + T L where[ v ] = [v sd v sq v rd v rq ] T [ i ] = [i sd i sq i rd i rq ] T T e = (3/4) poles L m (i sq i rd – i sd i rq ) p[i] = [L] -1 {[v] – [R] [i] – w r [G] [i]} pw r = poles (T e – T L ) / (2 J) For generating mode load torque is made negative. 18

19. 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. 19

20. 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. 20

21. 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 21

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