Evolution of microgrids with converter-interfaced generations: Challenges and opportunities

Distributed generation system operate with grid in islanding condition will damage equipment,affect the safe and stable operation of power system,even threaten the safety of line maintenance peopleTherefore,studying on distributed generation system in islanding condition has practical significanceThis paper presents an overview of islanding detection methods for distributed generation systemsThe paper classifies islanding detection methodsFinally,its study direction in the future is also looked ahead

Review of islanding detection methods for distributed generation

The increased penetration of distributed generation (DG), renewable energy utilization, and the introduction of the microgrid concept have changed the shape of conventional electric power networks. Most of the new power system networks are transforming into the DG model integrated with renewable and non-renewable energy resources by forming a microgrid. Islanding detection in DG systems is a challenging issue that causes several protection and safety problems. A microgrid operates in the grid-connected or stand-alone mode. In the grid-connected mode, the main utility network is responsible for a smooth operation in coordination with the protection and control units, while in the stand-alone mode, the microgrid operates as an independent power island that is electrically separated from the main utility network. Fast islanding detection is, therefore, necessary for efficient and reliable microgrid operations. Many islanding detection methods (IdMs) are proposed in the literature, and each of them claims better reliability and high accuracy. This study describes a comprehensive review of various IdMs in terms of their merits, viability, effectiveness, and feasibility. The IdMs are extensively analysed by providing a fair comparison from different aspects. Moreover, a fair analysis of a feasible and economical solution in view of the recent research trend is presented.

Comprehensive Review of Islanding Detection Methods for Distributed Generation Systems

A comprehensive review on intelligent islanding detection techniques for renewable energy integrated power system

In the smart-grid paradigm, since distribution systems are controlled by various independent operators, it becomes inevitable for all dispatchers to have a wide-area view of the network for situational awareness and protection. This visualisation is accomplished with the aid of protection (p) type micro-phasor measurement unit (μPMU) installed at the bus of the respective distributed generation (DG). One of the pressing issues with DG's is the concern of inadvertent islanding that disrupts orderly reconnection besides posing hazards to utility workers. In view of this, this study proposes a real-time inadvertent islanding detection by μPMU. The voltage and current phasors obtained from these μPMUs by discrete Fourier transform are further processed by Fortescue transform to compute the angle of sequence components. The absolute angle difference between positive and zero components is used to initiate signal for accomplishing intelligent islanding under islanded condition. The simulation results prove the method to be robust, computationally efficient, non-detection zone free and feasible. Most significantly, as measuring equipment and relay are already present in p type μPMU, therefore unlike other detection methods, no extra arrangements are required in this method making it economically viable and easy to implement.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-gtd.2018.5805

Smart inadvertent islanding detection employing p-type μPMU for an active distribution network

The augmentation in electricity demand, power system privatization as well as efficacy of renewable resources has paved the way for power system companies and researchers to exploit the field of grid connected distributed generation (DG) and its issues, islanding being a dominant one. Several research works have been conducted to mitigate the issues of islanding detection (ID). In context of this, the paper gives a comprehensive review of islanding issues, standard test systems, criteria and shifting of research trends in islanding detection methods (IDMs). The significant contributions pertain to categorization of IDMs, evaluation of non-detection zone (NDZ) for each test system, disquisition on evolution and advancement of IDMs and its comparisons based on criteria such as NDZ, run on time, nuisance tripping percentage, applicability in multi DG system and implementation cost to draw out the strength and shortcomings of individual methods that will come to aid to the companies or researchers for establishing the applicability and appropriateness of such method for their concerned domain.

/pdf/shifting-of-research-trends-in-islanding-detection-method-a-3k50ul9idz.pdf

Shifting of research trends in islanding detection method - a comprehensive survey

The advent of new technology and steep fall in cost of photo voltaic (PV) systems has rendered feed-in-tariff (FiT) scheme obsolete. Net energy metering (NEM) is gradually superseding the former as it promotes the growth of mini solar generations at every house. The primary objective of NEM is utilizing self produced renewable energy and to sell the excess to grid. However in spite of its numerous advantages, consumers are confused about its economic return. This paper proposes a model that will take customer's daily load curve and estimated renewable energy generation as input and give revenue saved and payback period as output depending upon the maximum generating capacity of solar panel. The entire modeling and analysis is done in MATLAB Simulink.

Optimum solar panel rating for net energy metering environment

Net energy metering (NEM) is a substitute for feed-in- tariff (FiT) for the encouragement and advancement of small scale distributed generation, especially in the residential sector. Currently, the applications of NEM are relatively confined but due to active role of many countries, it is gradually acquiring its foothold in the smart grid paradigm. However to make this policy successful in every parts of the world, the policies need to be revised and updated. This paper proposes a model for economic evaluation of net metering environment. Four cases are considered depending on house location considering only roof-top solar generation as renewable energy source. The difference in revenue earned and payback period among the four cases and the location biased nature of net metering are the major findings. The entire simulation is done in MATLAB simulink.

Location biased nature of net energy metering

In a typical microgrid (MG) structure, the requisite of load varies from hour to hour. On the basis of the rise and fall of the load demand curve, the power system utilities fix the rate of electric power at different times of the day. This process is known as time-of-usage (TOU)-based pricing of electricity. The hourly basis load demand can be categorized into elastic hourly load demand and inelastic hourly load demand. For the duration of the peak hours, when the utility charges more, the elastic loads are shifted to low demand hours by the demand side management (DSM) to save the cost. This rebuilds the total demand model on the pillars of demand price elasticity. Keeping in view the fact that the total load in an hour in an MG structure consists of 10% to 40% of elastic loads, the paper proposes an intelligence-technique-based DSM to achieve reduction in the overall cost of using loads in an MG structure. Seven different cases are studied which cover diverse grid participation and electricity market pricing strategies, including DSM programs. The results obtained for all the MGs showcase the applicability and appropriateness of using the proposed DSM strategy in terms of cost savings.

/pdf/intelligent-demand-side-management-for-exhaustive-techno-fmkxnrr3.pdf

Soham Dutta

Papers

Shifting of research trends in islanding detection method - a comprehensive survey

Smart inadvertent islanding detection employing p-type μPMU for an active distribution network

Optimum solar panel rating for net energy metering environment

Location biased nature of net energy metering

Intelligent Demand Side Management for Exhaustive Techno-Economic Analysis of Microgrid System