Relevance of anti-islanding algorithms for Grid-Tied Inverters and some new investigations Supervisor: Dr. Malabika Basu Presented by Sandipan Patra

Content Objectives Research Methodology ESPRIT Technique System Configuration Contribution Acknowledgement Question & Answer 9/16/2018

Damage to customer’s appliances Objectives Source: Making microgrids work [1] What is Islanding? Islanding refers to the condition in which a distributed generator (DG) continues to power a location even though electrical grid power from the electric utility is no longer present. Safety Concern Active islanding detection Problems caused by islanding Islanding detection methods Damage to customer’s appliances Passive islanding detection Inverter damage 9/16/2018 [1] Kroposki, B., Lasseter, R., Ise, T., Morozumi, S. Papathanassiou, S., and Hatziargyriou, N., “Making microgrids work”, IEEE Power and Energy Magazine, Vol. 6, Issue 3, pp. 40-53, 2008.

Active Islanding Impedance Measurement Detection of Impedance at a Specific Frequency Slip-mode Frequency Shift Frequency Bias Sandia Frequency Shift Sandia Voltage Shift Frequency Jump ENS or MSD (a device using multiple methods) Active methods generally attempt to detect a loss in grid by actively trying to changing the voltage and/or frequency of the grid, and then detecting whether or not the grid changed.

Passive Islanding Over/under voltage and frequency trip settings Voltage and frequency relay functions Set a V/F window – if conditions are outside window, then DR trips Non-detect zone (NDZ) exists between trip points Amendment 1 (IEEE 1547a) allows for adjustable clearing times Rate-of-change-of-frequency (ROCOF) New Voltage and Frequency Trips Settings from Amendment 1 of IEEE 1547-2003 [2] [2] IEEE Standard for Interconnecting Distributed Resources with Electric Power Systems," IEEE Std 1547-2003, July 28 2003

Research Methodology Any kind of disturbances to the system introduces a transients in the system and the nature of these transients are depends upon the type of disturbances. Frequency profile of non-islanding events is oscillating in nature whereas islanding event frequency profile is monotonically increasing or decreasing. A new anti-islanding protection scheme based on the estimation of transient’s frequency is developed. The transient’s frequency for islanding event increases as power mismatch decreases and it reaches up to its maximum value (5 Hz) when power mismatch is zero Fig : Behavior of frequency at PCC Transient’s frequency of non-islanding event (Load Switching, capacitor bank switching, distribution line faults, etc.) is much higher than 5 Hz. So islanding event occurs, when the transient’s frequency lies between zero to 5 Hz. 9/16/2018

Research Methodology Flow chart of proposed anti-islanding protection using the ESPRIT technique 9/16/2018

System Configurations 9/16/2018

Research Contribution Case Study 1: large power mismatch 9/16/2018

Research Contribution Case Study 2: Small power mismatch 9/16/2018

Research Contribution Case Study 3: Load switching (non-islanding event) 9/16/2018

Research Contribution Case Study 3: Capacitor switching (non-islanding event) (c) (b) (a) (d) Fig. Capacitor switching (non-islanding event) with (a & c) Proposed ESPRIT based method and (b & d) Wavelet based method

Research Contribution Case Study 3: Effect of harmonics (non-islanding event) (c) (a) (b) (d) Fig. Effect of 13 and 17 order harmonics on (a & c) Proposed ESPRIT based method and (b & d) wavelet based method

Conclusion Proposed ESPRIT based anti-islanding scheme is found to be very effective in discriminating between islanding detection and other disturbances. NDZ is very small in the proposed scheme and it avoids nuisance tripping because of other transients. 9/16/2018

Acknowledgement This work has been carried out with the support of Science Foundation Ireland Electrical Power Research Centre,  Dublin Institute of Technology 9/16/2018

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