The document proposes a fault protection scheme for a smart DC microgrid system with a ring topology. It describes existing protection challenges in DC microgrids due to power electronic devices limiting fault currents. The proposed scheme uses local intelligent electronic devices and a least squares technique to estimate fault inductance and discriminate between forward and reverse faults, enabling identification of internal faults. Simulation results demonstrate the performance of the proposed protection scheme.

1. Title

2. ABSTRACT
• This project describes the fault protection in dc microgrid system, This microgrid system designed with ring structure
topology
• In a smart DC microgrid, power electronic devices limit the current during fault and therefore, an overcurrent based
relaying scheme cannot provide required sensitivity and selectivity for such a system
• The electronic equipment used in DC microgrids is in essential need of more secure protection against short
circuit faults.
• Due to the high current at the time of fault occurrence, the whole system might be de-energized which would
have a severely negative impact on the entire system.
• An effective method to detect, isolate, and protect the DC microgrid system against the effects of short circuit
faults is extremely important protection. This protection network is distributed all along the DC microgrid system
protecting the entire microgrid network and is connected to the other protective devices in the system.

3. INTRODUCTION
 Developing renewable energy devices and power storage systems in the last two decades made them
more popular than ever, and they are recognized as sustainable power systems
• to integrate renewable energy sources (RESs); photovoltaic and wind turbines into existing distribution
networks. Growth of energy demand and environmental concern urge for RESs in smart grid initiatives
• Based on the connection of equipment types, networks in the microgrid can be AC, DC or a combination
of the two DC network is more feasible for a demarcated power system
• In a DC network, the common fault is of pole-to-ground type and this is because of physical damage,
aging or severe electrical stress in cable

4. EXISTING SYSTEM
• In existing system there is no protection circuit on micro grid system
• Three phase breaker has been deployed on the system for protection of fault in the system
• The DC power systems do not have problems like synchronization, reactive power and low
efficiency
• Internal faults in converter include failure of switches such as insulated-gate bipolar transistor
(IGBT)
• Fault in DC network with parallel converters is the more severe one. The DC link capacitor of
converter and small cable impedance cause severe overcurrent and undervoltage during a fault.

5. DISADVANTAGES
• require reliable communication channel
• High stress on electrical system
• large steady state value

6. PROPOSED SYSTEM
• The proposed system is a protection scheme for smart DC microgrid with ring configuration is proposed.
• Using local intelligent electronic device (IED), voltage and current data during fault
• a protection scheme for smart DC microgrid with ring configuration is proposed.
• Using local intelligent electronic device (IED), voltage and current data during fault, a LS based technique
estimates the inductance of the fault path which is able to discriminate forward and reverse faults with respect
to the IED. This fault direction information is communicated to the other end IED of a line segment. Using
the local and other end fault direction information, each IED identifies any internal fault of the line segment
correctly. Signals generally being contaminated by noise in a system, as proposed method uses least square
filtering, it is able to estimate the seen inductance in IEDs accurately

7. Protection circuit

8. Theory model
• Fault characteristic and effects
there are two kinds of short circuit fault in DC microgrids. The majority of these faults are line to
ground fault due to the component or segment failure or lightning.
It rarely happens line to line fault because of impact or other mechanical reasons, When a short circuit
fault happens in the DC microgrid, the fault resistance tends to zero and the current tends to become
infinite

9. Solar system

10. Algorithm flow for fault protection

11. Advantages
• Reduced power loss
• Fault protection
• Reduced voltage loss on the distributed system
• Stability

12. Microgrid system

13. Block diagram
• This block diagram describes the microgrid system
• A short circuit fault in DC network is a severe condition for converters and the IGBTs can be blocked for self
protection letting reverse diodes exposed to overcurrent
• construction of a DC microgrid consists of PV solar panels, battery storage, AC main grid and loads. PV solar
panels are working with MPPT converters for maximum power point tracking and maximum power capturing
[Battery storage has a back-up role in the system;
• it is equipped with DC/DC bidirectional converter; those batteries are charged through DC bus with PV solar
panels or AC main grid; and they discharge at night for load consumption and loss of mains.
• In case of insufficient power supply, Load Shedding Control Strategy (LSCS) is applied to balance the load

14. Simulation results

15. parameter

17. Battery model

19. Dc load

20. Ac load

21. current

22. Power response

24. conclusion
• DC microgrid protection with ring configuration is challenging because of current limiting control in
converters and bidirectional power flow
• The performance of the method is found to be better for high resistance fault and for faults during high
loading conditions as evident from the comparative assessment.
• The method uses LS technique for estimation of seen inductance at each IED during fault from which forward
and reverse faults are discriminated. This fault direction information is communicated to other end IED for
identification of internal fault if any in that line segment

25. Future scope
• In future work same system is implemented by the machine learning algorithm
• An Artificial Neural Network, fuzzy logic based machine learning algorithm is defined by only
one circuit breaker that will receive data from current modules in the DC microgrid.
• New techniques for DC circuit breakers in low voltage DC systems are studied with
semiconductors using solid state circuit breakers which consist of two insulated gate bipolar
transistors, gate turn-off thyristors and integrated gate-commutated thyristors with parallel diodes.
• These devices are widely used in most DC circuit breakers and converters which act in just a few
milliseconds to cut off the power. Therefore, it is used as an efficient protection scheme for a DC
microgrid.

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