1. Control Schemes for Distribution Grids with Mass Distributed Generation
AUTHOR: UMAIR SHAHZAD

2. AIMS AND OBJECTIVES
To study the control schemes for distribution grids with large wind energy penetration
Grid + Synchronous generator + Loads
Two Synchronous generators + Loads
Active & Reactive Power Sharing
Droop Control
Introducing Wind (Constant + Variable)

3. DISTRIBUTED GENERATION
Distributed generation is the generation of electrical power using a small source which is not part of the large central power system and which is located in close vicinity of the load. Also known as decentralized, embedded or dispersed generation.
Types
Reciprocating Engines
Micro turbines
Fuel Cells
Photovoltaics
Wind Power

4. Reciprocating Engines
Oldest technologies
Fuel source: diesel/natural gas
Engine design is vital for increased efficiency

5. Micro turbines Small turbine + compressor + generator
Low emissions, less maintenance
High cost, reduced efficiency
Solution: recuperators
Common types: simple cycle, combined cycle

6. Fuel Cells Fuel source: propane/natural gas Low emissions
Less maintenance (no rotating parts)
High cost
Types include PAFC, PEMFC, AFC

7. Photovoltaics Modular Low emission rates, less maintenance
High cost of purchase and installation
Remote locations

8. Wind Power Low CO2 emissions, low pollution effects
Maintenance of gearbox & rotor
Birds and bats
Unpredictable wind
Solution: battery storage systems

9. Why to use Distributed Generation?
Environmentally Friendly
Power to local load
Opportunities for players in energy market

10. MICROGRID
A group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid (and can) connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode.
The basic function of micro-grid is to maintain stable operation under various faults and factors which can disturb the network stability.

11. MODES
Grid Disconnected
Grid Connected

12. Differences between main grid and microgrid
Modular.
There are many unconventional generators in a microgrid like wind power, photovoltaic or fuel cells.
Besides power, microgrid has the ability to supply heat. It can utilize waste heat using CHPs, hence, giving a rise to the overall efficiency of the network.

13. Advantages of using microgrids
CHP
Modular
Large variety
Continuity of supply
Environmentally friendly
Jobs
Minimum losses

14. Simulation Work
Grid+SG+ Resistive Load

15. Behaviour of Active Powers
Active power of synchronous generator= 0.5 MW

16. Behaviour of Active Powers
Active power of main grid= 0.5 MW

17. Calculation of Load Active Power
Load RMS Current= 52.5 A

18. Load RMS Voltage= 6353 Volts

19. Load Active Power Calculation
Load Power= 3*Vrms*Irms*cos (phi)
P= 3*6353*52.5*1= 1 MW
Active Powers of the System:
GRID+SG= LOAD

20. Behaviour of Reactive Powers
Reactive power of grid= -36 KVARs

21. Reactive Power of synchronous generator= 36 KVARs

22. Investigation of Load angle
Synchronous Generator + Resistive Load

23. Simulation Results
As resistance increases, current decreases and load angle decreases.
Load Resistance (Ohms)
Load Current
(Amps)
Load Angle
(Degrees) 40 20
1.16 50
16.2
0.96 70
11.6
0.73 15
52.96
2.815 5
135
8.214

24. Phasor Diagram
Phasor diagram E
jIXs V
LOAD ANGLE

25. Investigation of Load angle
Grid + SG + RL Load

26. Simulation Results
As resistance increases, current decreases and load angle decreases.
Load Resistance
(Ohms)
Load Current
(Amps)
Load Angle
(Degrees) 40 66
1.4 50 57
1.2 70 43
1.1 5 94
4.34

27. Parallel operated synchronous generators
Why operated in parallel?
Reliability
Flexibility
Supply a much bigger load than a single machine
Conditions for paralleling
Same RMS line voltages, phase angles, phase sequences and frequency

28. Simulations for 2 synchronous generators
2 SGs + Resistive Load

29. Active Power of SG 1 (1 MW)

30. Simulations for 2 synchronous generators
2 SGs + Resistive Load

31. Simulation Results Active Power of SG 1 (0.5 MW)

32. Active Power of SG 2 (0.5 MW)

33. Reactive Power of SG 1 (-21KVARs)

34. Reactive Power of SG 2 (21 KVARs)

35. Summary of Results SG1 Active Power= 0.5 MW SG2 Active Power= 0.5MW
Load Active Power= 1 MW
SG2 can be made to run at 0.7 MW , SG1 will then give out 0.3 MW.
SG1 Reactive Power= -21 KVARs
SG2 Reactive Power= 21 KVARs
Load Reactive Power = ZERO

36. Load Transients
Resistive Load Transient

37. Graphical Representation of Resistive Load Transient

38. Resistive-Inductive Load Transient

39. Graphical Representation of Resistive-Inductive Load Transient

40. Droop Control of Synchronous Generators
Typical Droop Graphs (P-F and Q-V)

41. Simulations for Droop Control
2 SGs + RL Load

42. Q-V Droop SIMULATION RESULTS. Load Q= 210 KVARs K1 K2 Q1 (VARs)
0.01
1.05e5
0.05
3.02e4
1.51e5
0.001
2.5e5
2.5e4

43. P-F Droop SIMULATION RESULTS. Load P= 0.96 MW K1 K2 P1 (W) P2 (W) 0.01
0.05
4.7e5
5e5
0.001
4.95e5
4.75e5

44. Variations in Inductive Load
Load inductance is varied. Reactive power sharing is observed.
Load Inductance (H)
Q1 (VARs)
Q2 (VARs)
Qload
(VARs)
0.001
1555
3110
0.1
0.1e6
0.2e6
0.5
0.16e6
0.32e6

45. Simulations involving Wind Power
Wind Active and Reactive Power introduced through Id and Iq

46. Simulations and Results
Constant Id (20A) and zero Iq
Behaviour of Active Powers was observed.
Active Power of SG 1 (0.13 MW)

47. Active Power of SG 2 (0.5 MW)

48. Load RMS Phase Voltage

49. Load RMS Phase Current

50. Calculation of Wind Active Power RMS Phase Voltage (6350 V)

51. RMS Phase Current (19.39 A)

52. Wind Active Power is 3*6350*19.39=0.37 MW
In short, Active Powers of the system:
SG 1= 0.13 MW
SG 2= 0.5 MW
WIND= 0.37MW
LOAD= 1 MW
SG1+SG2+WIND= LOAD

53. Relationship between Iq and Reactive Power
Consider the network:

54. Reactive Power of SG 1 (150 KVARS to 300 KVARs)
Step Iq (15 A to 30A at 3s) is applied instead of constant.
As Iq is doubled, reactive powers of SGs doubled.
Reactive Power of SG 1 (150 KVARS to 300 KVARs)

55. Reactive Power of SG 2 (125 KVARS to 250 KVARs)

56. Variable Wind Id was input as variable data Iq was set at zero
Time (seconds)
Wind Speed (m/s)
0.0
13.2
0.1
13.9
0.2
14.2
0.3
14.8
0.4
16.5
0.5
16.7
0.6
18.4
0.7
20.1
0.8
0.9
11.9
1.0
11.2

57. Trend of Active Powers
Active power of SG 1 decreases up to 0.7 s, then increases
After 1s, SG 1 = 0.29 MW, SG 2=0.5 MW, Wind= 0.21 MW (3*6300*10.76)

58. Active Power of SG 2 (0.5 MW)

59. Summary of Results Active Powers: SG 1= 0.29 MW SG 2= 0.5 MW
WIND= 0.21 MW
LOAD= 1MW
SG1 + SG2+ WIND= LOAD

60. Future Work
In-depth investigation and evaluation of various frequency and voltage control techniques under grid-connected and grid-disconnected modes.
Observing the transition phenomenon closely from grid-connected mode to grid-disconnected mode and vice versa. Observing the same under high penetration of wind power.
Researching, designing and implementing protection schemes for microgrids.
Operation of microgrids under unbalanced and non-linear loads.

61. Conclusions Theoretical Background and development projects discussed
Active & Reactive Power sharing, Droop control and load transients were investigated
Wind introduced and behaviour of the system observed