INTERACTIVE DISTRIBUTED GENERATION INTERFACE FOR

FLEXIBLE MICRO-GRID OPERATION IN SMART

DISTRIBUTION SYSTEMSAuthors:Alireza Kahrobaeian and Yasser Abdel-Rady I. Mohamed

IEEE TRANSACTIONS ON SUSTAINABLEENERGY, Vol. 3, No. 2, 2012, pp. 295-305

BY: HADI ALRAKAHCSU ID: 2495128

Outline

1.Introduction- Smart Grid2. Concept of Distributed Generation3. Impact of DG on Power Grid4. Study System Overview 5. Fault on Source Bus 6. Conclusion and Future Work

1. Introduction-Smart GridSmart stands for Self Monitoring Analysis and Report Management.

Grid is an electrical interconnected network for delivering electricity by maintaining frequency as constant. Features:

• Proactive management of electrical network during emergency situations.

• Better demand supply / demand response management, better power quality, reduce carbon emissions.

2. Concept of Distributed GenerationDG Definition: Distributed Generation is the energy generated or stored by a variety of small, grid-connected devices referred to as distributed energy resources (DER).They are not controlled by the Electrical Utilities rather it is done by the one who is producing it individually.

Ex: It typically uses renewable energy sources, including, but not limited to, biomass, biogas, solar power, wind power etc.

Transformation of the Grid

3. Impact of DG on Power Grid • The DG can serve critical loads when the

main grid has been disconnected forming an islanding effect.

• Islanding effect: It refers to a condition in which the DG system continues to supply power to some critical loads even when the main electric grid is disconnected from the system due to fault thus increasing the reliability.

4. Study System Overview

System Description • The Study System is taken from IEEE 1559

for low voltage applications.

• It is a 2.4 kV Distribution System that has 2 AC loads ,one being an inductive load of 8MVA and a nonlinear load is a three-phase diode rectifier.

• It is a Generalized model for which DG’s can be connected and operated either in parallel or isolated mode to serve sensitive loads.

Modes of OperationIn the System taken DG’s are operated in two modes

1)Grid Connected Mode - Control Active Power (P) under P-Q bus. - Control Voltage(V) under P-V bus. 2) Isolated Mode(Islanded mode) -Control Voltage fluctuations under P-V bus.

Grid Connected mode-Step load change

Isolated Mode

5. Fault on Source Bus •  When a fault occurs at Bus BR, the protection relay disconnects the main source from the system.

•  The voltage at the DG bus also does not stabilize after the fault as shown in Fig. (b).

• Active power from the main source bus is reduced to zero as system shown in (c).

Results • The total harmonic distortion(THD)of the

phase- voltage is 0.67% and 0.81% before and after adding the non-linear load respectively.

• The active power command experiences a step change from 5 to 10 kW a t = 1s.

• Islanding occurs at 0.82s and the frequency of the system starts to drop.

• The ability of DG to form an islanded system may be beneficial to provide continuity of service if suitable measures are taken.

• However, formation of an island requires further care and suitable a load shedding and Var compensation strategy may be required.

• The old adage of disconnecting the DG is too protectionist, further care is required when resynchronization back.

6.Conclusion

• The Author didn’t consider the security constraints when the DG is operating when the main generator is isolated due to fault.

• The type of elements used for Commutation is not discussed in the paper.

• It didn’t explain the region in case wherein the DG need to shut down due to fault in that particular region.

Critical Assessment

• We need to define regions for the DG operation during normal mode and Fault condition.

• The efficiency of the DG’s need to checked and the optimal selection based on type of load it is feeding.

Future Work