1,720,961 research outputs found
Microgrid fault detection technique using phase change of positive sequence current
No full textThis article presents a new algorithm for fault detection in grid-tied microgrids with inverter-interfaced distributed generators (DGs). To support the Grid codes, the DGs require a low voltage ride through (LVRT) capability. The control strategy used in the DGs results in large changes in the fault characteristics of the microgrid. Hence, it is required to study the fault characteristics of the DGs in a microgrid under various operating conditions. The study presents fault detection for microgrids with PQ-controlled DGs having LVRT capability under different DG voltage and different fault conditions (high impedance and low impedance). The fault location has been identified using the phase change in the positive sequence current at specific DG voltages. The reliability of the proposed scheme has been validated under diverse fault conditions through extensive simulations in the Matlab/ Simulink environment, and the comparison with other fault detection techniques proves the efficacy of the proposed scheme for fault detection in microgrids
A new Lissajous-based technique for islanding detection in microgrid
No full textThis study presents a novel technique for islanding detection in microgrid based on Lissajous figure of voltage and current signals. The Lissajous figure reveals distinct pattern during islanding which can segregate the islanding event from other non-islanding disturbance events such as switching transients and faults. Lissajous figures have been considered as images to capture the characterizing patterns in their shapes. The area of the Lissajous figure has been considered for successive intervals to develop an index mathematically and an appropriate adaptive threshold value of index has been formulated to detect the islanding phenomenon. The proposed technique does not require the information about the network configuration. The efficacy of the proposed technique has been established through fast islanding detection with load inside the non-detection zone (NDZ) and under the condition of complete match between the distributed sources and the load. To establish the efficacy of the proposed technique, comparative analysis has been carried out with other recent islanding detection techniques
An optimization based resilient control strategy for voltage unbalance compensation in grid connected microgrid system
No full textA novel two stage multi-objective control strategy for optimal voltage unbalance compensation in low voltage microgrid systems consisting of inverter interfaced distributed generators (IIDGs) has been presented in this research. To ensure continuous and safe operation of the IIDGs during unbalanced voltage sags, the proposed control strategy supplies the optimal positive sequence voltage support and performs voltage unbalance compensation considering the current limitation of the inverters. The control strategy also ensures that the DGs deliver maximum allowable active power during voltage sag. The positive and negative sequence quantities of the IIDGs are controlled in such a way so that these objectives can be achieved simultaneously. The DGs are operated in coordination with each other to maintain the voltage profile as desired by the grid operator. Prioritisation of active power and unbalance compensation can be set depending upon the requirement of the customer. Under severe grid imbalance condition, the proposed technique can raise the positive sequence voltage to near nominal value from below 0.9 per unit maintaining all phase currents of DGs within safety limit.To solve the optimization problem and to generate the optimal references for the DG control unit, artificial cooperative search algorithm has been utilised. The two stage control strategy includes a local control for each DG, which coordinates with the central control to provide the optimal references for all the DGs. The multi-objective control strategy has been tested under different operating conditions and implemented in real time digital simulator to ensure the robustness and effectiveness of the proposed approach.</p
Multi-objective pareto optimal unbalance voltage compensation in the microgrid
No full textVoltage unbalance control plays an important role in maintaining the power quality standard in microgrid. This paper presents a multi-objective control strategy to realize optimal voltage unbalance compensation in a multibus microgrid, satisfying customized power quality requirement of the consumers at different buses. The distributed generators (DGs) in the microgrid share the compensation effort cooperatively to satisfy the power quality standard at different buses. Multi-objective Artificial Cooperative Search Algorithm (MOACS) has been proposed to solve the multi-objective pareto optimization problem. The algorithm assigns compensation reference to all the DGs so that the DGs can accordingly compensate the negative sequence voltage at different buses and thereby mitigate voltage unbalance. The effectiveness of the proposed scheme has been established through the results obtained from simulation and real time digital simulator
A Lissajous based technique for fault detection and faulty phase identification in transmission line
No full textThis study presents a technique for fault detection and faulty phase identification in transmission lines based on the change in the Lissajous pattern. Lissajous figure reveals distinct pattern during faults and can discriminate the faulty condition from the normal operating condition of the line. Fault Index has been calculated considering a quarter cycle moving window and Euclidean norm. Faults can be detected and classified within half cycle from the inception of fault and accurate results have been obtained for fault resistance upto 50 ohms. The ten types of faults have been simulated throughout the length of the transmission line and a threshold value offault index has been considered for fault discrimination. It has been observed that the fault indices of the faulty phases rise above the threshold value within half cycle of fault inception
A multi objective approach for optimal design of solar/ wind/ biomass/ battery-based grid connected microgrid system
No full textDue to the depletion of fossil fuels the dependency on the reliable and ecofriendly alternative sources has increased. The renewable energy sources have become alternative sources for the fossil fuels. However, there are some issues with the renewables which include uncertainty, reliability, high cost and intermittency of the sources. By integrating the multiple renewable sources together these issues can be minimized. In this study grid integrated wind, solar, biomass and battery based microgrid system is proposed using a multi objective artificial cooperative search algorithm (MOACS) with the objective to minimize the annual life cycle costing (ALCC) with high reliability (minimizing the loss of power supply probability (LPSP)). Different case studies have been presented and the comparative study proves the supremacy of the proposed approach
Multi‐objective optimization of photovoltaic/wind/biomass/battery‐based grid‐integrated hybrid renewable energy system
No full textAbstract The variable nature of the renewable energy resources (RES) complicates their modelling, operation, and integration to the grid. Therefore, it is difficult to choose optimal RES with a proper energy storage system (ESS) for the economic and reliable operation of the grid‐integrated hybrid renewable energy system (HRES). There is a need to solve this optimal HRES problem using efficient algorithms due to the high cost and model complexity involved. In this study, optimal photovoltaic, wind, biomass, and battery‐based grid‐integrated HRES is proposed using a multi‐objective artificial cooperative search algorithm (MOACS) to minimise annual life cycle costing and loss of power supply probability. ESS is chosen to provide a backup power supply for at least 30 min during peak load condition. A probabilistic approach is used to consider the time‐varying nature of the RES and load while solving optimal HRES design problem by employing MOACS. A comparative analysis is provided at the end, which shows that MOACS can provide a better optimal design of HRES
Optimization based voltage unbalance compensation in the microgrid
No full textVoltage unbalance has become a common issue in the low voltage ac microgrids due to the rapid enhancement of penetration of single phase loads and unbalanced loads into the distribution system. The negative sequence voltage of the load buses increases due to the presence of unbalanced loads which is not desirable as it causes voltage quality reduction in the system which leads to extra power loss and even makes the system unstable by creating disturbances during the system operation. Therefore, in this study an optimization based unbalance voltage compensation approach for grid connected microgrid is proposed. The distributed generators (DGs) in the microgrid are used as compensating devices and Artificial Cooperative Search (ACS) algorithm is used to generate the optimal references for the DGs. The voltage quality at each load bus can also be customized according to the consumer
Fault detection method for inverter interfaced distributed generators based microgrid
No full textA microgrid is a small power distribution system consisting of a cluster of low-power generation units (micro energy sources) capable of operating independently, loads, energy storage, and energy conversion devices with associated protection and control units. Unlike traditional microgrids, the micro sources in all microgrids are inverter-interfaced distributed generators (IIDGs), in which the fault currents are 1.2-2 times the rated current. To ensure the stable operation of the microgrid requires to detect the faults within the minimum possible time. The data collected from Waveform Measurement Units (WMUs) are widely used to detect disturbances. When an event occurs, WMUs provide GPS-synchronized measurements of voltage and current waveforms in the time domain captured during the event. Given such data, a Lissajous curve can be developed, which is a graph constructed by plotting one waveform versus another. By utilizing this phenomenon, a new algorithm has been developed to detect and locate faults within the microgrid
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