Browsing by Author "Gaonkar, Dattatraya N."

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Islanding Detection Using Computational Intelligence Techniques in a Smart Distribution Network
(National Institute of Technology Karnataka, Surathkal, 2020) Goud, M Santhosh Kumar.; Gaonkar, Dattatraya N.
Distributed generation (DG) offers solution to the ever increasing energy needs by generating the energy at the consumer end, in most cases by means of renewable energy sources. A microgrid with DGs will result in an enhanced performance in terms of continuity of the power supply for consumers. Microgrids may operate either in grid{connected or islanded mode. Islanding detection is one of the most important aspect of interconnecting a DG to the utility. Several islanding detection methods have been proposed over the years to improve the islanding detection in terms of detection time, accuracy. However, with the upcoming trends, such as smart grids, there is an imminent need for incorporating intelligence to the islanding detection methods. Also, it is important for the islanding detection methods to perform well at near zero power mismatch conditions and noisy conditions. This research work proposes islanding detection methods based on image classification techniques. Time{series data from point of common coupling is acquired and then converted to an image to enable this. A dataset for islanding detection based on several islanding and non{islanding events is created to be used in training and testing the machine learning and deep learning models. Three islanding detection methods are proposed in this research work. The first method is based on HOG feature extraction from the image and SVM classifier. The second method is based on transfer learning method. The third islanding detection method is based on custom designed CNN for islanding detection. In addition to islanding detection, a feature for early islanding detection is also proposed in this research work. Early islanding detection is proposed by monitoring the fault and normal conditions. Once a fault occurs, the time window between the operation of relay contacts and the opening of circuit breakers is utilized to detect the islanding event. All the methods are tested with the islanding dataset that is created which includes near zero power mismatch conditions and noisy data. The proposed methods demonstrate the potential of image classification techniques for islanding detection.
Modeling and Performance Analysis of Microgrid with Wind and Photovoltaic Based Distributed Generation Systems
(National Institute of Technology Karnataka, Surathkal, 2016) N. S, Jayalakshmi; Gaonkar, Dattatraya N.
The advancement in technology, environmental concerns, emerging power markets and deregulation of electric power utilities are leading to increased interconnection of distributed generators (DGs) to the utility system. The different types of DGs, such as microturbines and fuel cells in addition to the traditional solar and wind power are creating significant new opportunities. The benefits of interconnection of these generators are improved reliability, power quality, efficiency, alleviation of system constraints along with the environmental benefits. Due to the growing momentum towards sustainable energy developments and considering these benefits it is expected that a large number of DG systems will be interconnected to the power system in the coming years. Interconnecting large number of small DG systems with diverse characteristics to low voltage network causes many problems. The microgrid is a section of network operating in a systematic way, comprising sufficient generating resources in the autonomous or grid connected mode in an efficient and controlled way. The microgrid has more control flexibilities and larger power capacity to fulfil power quality requirements and system reliability. Along with generation sources microgrid also consists of storage devices such as flywheels, batteries and super capacitors. The wind and photovoltaic (PV) power generation are two of the most promising renewable energy technologies. Hybridizing wind and solar power sources together with storage batteries to cover the periods of time without sun or wind provides a realistic form of power generation. Currently variable speed drives (VSD), lighting, batteries and electronics constitute major part of the load. The DC power can be supplied to these loads from microgrid system with usage of minimum converters with decreased losses. In this research work, a microgrid with wind and PV as the energy resources with single 3 phase inverter considering both DC and AC loads, which can reduce the multiple conversion stages has been implemented. Both wind generator and PV panels are controlled to operate at their maximum power point. The wind power system presented in this work uses the permanent magnet synchronous generator (PMSG), because of its property of self excitation, which allows operation at a high power factor and high efficiency. It also results in smaller size, minimum weight and higherii torque to size ratio. This work mainly focuses on mathematical modeling, control schemes for operation of microgrid with energy storage devices for both isolated and grid connected mode under various generation and load conditions. Based on the dynamic component models, a simulation model for the microgrid system has been implemented in the Matlab/Simulink environment. In this work, the load following performance of microgrid system is studied in an isolated mode of operation. The microgrid model with integration of wind and PV energy system with battery energy storage devices has been implemented. The battery is thus controlled to provide the deficit power when the combined wind and PV energy sources cannot meet the net power demand. All three energy systems are connected in parallel to a common DC bus line through three different DC/DC converters. The performance study is analyzed with consideration of DC loads, nonlinear and induction motor loads for variable nature of the individual DG source. In this thesis the simulation results for evaluation of the performance of the microgrid system in grid interconnected mode of operation using case studies are also presented. For grid integrated microgrid system, grid behaves as backup energy source. The overall power management strategy for coordinating the power flows among the different energy sources is presented in the thesis. The results show that the overall power management strategy is effective and the power flows among the different energy sources and the load demand is balanced successfully. Also the performance of the microgrid system is studied under grid perturbations conditions. The common grid perturbations considered in this study are balanced voltage dip, voltage unbalance and harmonic distortions. The simulation result reported in this work also shows that, the performance of the model presented is not affected by the grid disturbances considered. The last part of the dissertation focuses on power smoothing of the grid integrated microgrid system using ultracapacitors, also with combination of battery and ultracapacitors. The battery performance can be improved in terms of the power density by combining ultracapacitors with batteries which are typically low power devices. The power obtained from wind and PV system varies with the changes in weather conditions. Especially in weak power systems with large penetration of intermittent renewable energy (RE) generation sources into the utility grid, mayiii introduce adverse effects on the utility grid. To compensate or absorb the difference between the generated power and the required grid power, energy storage systems are used. Most of the technical literatures discuss the control performance of battery storage devices used for power smoothing of renewable power sources such as wind or PV power system. However in this research, the control schemes have been developed for power smoothing of the grid integrated microgrid system using ultracapacitors and combination of battery and ultracapacitors. In order to observe the real-time performance of energy storage system in smoothing the output power fluctuations, the practical site data for wind speed and solar irradiation are considered. The final result of proposed control strategy is a smooth and ramp controlled power output that can be injected to the grid.
Operation and Control of a Microgrid with Distributed Generation Systems
(National Institute of Technology Karnataka, Surathkal, 2020) D, Chethan Raj.; Gaonkar, Dattatraya N.
The energy has always played a crucial role in the development and progress of human society. People have long been aware of the drawbacks of traditional fossil energy, such as the limited resources, resulting in environmental pollution and other defects. However, due to the needs of social development and the constraints of backward technology, people have to use fossil energy as the main energy source. In recent years, with the rapid development of science and technology, how to effectively use renewable energy to generate electricity has become the focus of attention in many countries. Because of its unique advantages in the use of new energy, microgrids have received more and more research and development. The distributed power generation system based on microgrid technology is an important way to develop renewable energy, increase the reliability of power supply, and expand the capacity of the power supply system. The power supply of the distributed power system can be formed by a variety of energy sources through power conversion. The power supply units of the distributed power system are distributed and are all connected to the AC grid bus. The power supply unit of distributed generation micro-power system is generally a parallel inverter, and there are many parallel modes of inverter and the parallel mode of inverter power without interconnection line is especially suitable for distributed power generation system with grid-connected inverter. The ideal distributed generation microgrid system includes parallel DG inverter power modules, output line impedance, AC bus and loads connected to the AC bus. The DG inverter is the core of the distributed power generation system, which is responsible for transforming the distributed energy into electric energy and realizing the parallel network operation of the system.This thesis studies the droop controlled distributed generation inverters power decoupling and the restoration of frequency and voltage under resistive and inductive impedance microgrid environment. Summarized the research background, definition and characteristics of microgrid. Summarizes the existing control structure of the microgrid. The classification, comparison and analysis of control methods for power electronic converters,vi especially distributed generation inverters in microgrids are focused on. The topology of the distributed generation inverter main circuit and the filter circuit was chosen and filter parameters were designed. Then the mathematical model of distributed generation inverter in different coordinate were established. Since the output voltage strategy and output impedance of an distributed generation inverter always have an important influence on the DG inverter parallel system and power distribution. The instantaneous voltage closed-loop control in three-phase stationary coordinate and the inverter output voltage decoupling control strategy in dq rotating coordinate were analysized, in order to reduce variable numbers, while ensuring the DG inverter output voltage tracking with no difference to the reference voltage, the DG inverter output voltage control strategy based PI controller in dq coordinate is implemented and the influence of the controller parameters on closed-loop transfer function of output voltage and inverter equivalent output impedance were analysized. The droop control is widely employed when multiple distributed generation inverters operate in parallel. However, due to inconsistent line impedance and the local load, there exists power sharing errors when the droop control is adopted, thereby reducing the efficiency of the system. In addition, there is a coupling between the active power and reactive power with the direct droop control, which affects the stability of the system. Though the traditional power decoupling control is able to realize power decoupling, the actual real power and reactive power cannot be shared equally. To deal with the power sharing and power coupling problem, this chapter explicitly analyzes the causes of the power sharing error and power coupling with the direct droop control respectively, quantizes the power sharing error and the extent of power coupling and also gives the basic solution to reducing the power sharing error and solving the problem of power coupling. To solve the inaccurate power sharing problem of the direct droop control, virtual inductance is adopted. By adding the virtual inductance, can decouple the active and reactive power, but also achieve accurate power sharing. The simulation results verify the accuracy and effectiveness of the adopted control scheme. Using direct droop control, the active power and reactive power can be decoupled when the line impedance is mainly inductive. However, it is not applicable to the microgrid with low voltage when the line impedance is resistive. As a result, thevii active power and reactive power will be coupled and errors in preset ratio of power sharing will arise. Aiming at solving the problem about the inapplicability of direct droop control in low voltage micrigrid, this chapter implements reverse droop control. The influence of transmission impedance of distributed generation inverter to public load on power distribution, introduces virtual resistor and then uses reverse droop control strategy to distribute load in low voltage distributed power generation system. Analyzes the conditions that need to be met to accurately share the load according to the ratio of rated capacity for inverter power supply. In the actual distributed generation system, due to the distributed location of the distributed inverter power supply, the impedance of the line is uncertain and the traditional reverse droop control has certain limitations. The simulation model of DG inverter parallel operation is built under the matlab/simulink environment, the reverse droop control and the improved power allocation strategy using virtual resistance are simulated and compared, the correctness and validity of the adopted improved strategy are validated. The traditional centralized control method cannot solve the problem of the various modes of microgrid operation, for example, the probem of controlling the microgrid systems induced by hard to collect information signals and low controllable. But the distributed secondary control method based on direct and reverse droop control has obvious advantage to solve the problem of parallel connected DG inverters operation. Aiming at the problem of voltage and frequency differences caused by the direct and reverse droop control and considering the actual situation of inductive and resistive line impedance mismatch, this thesis proposes a distributed secondary control. The simulation verifies that the proposed distributed secondary control method can guarantee the voltage amplitude and frequency recovery.
Performance Analysis and Control of HVDC Links In Multi-Machine Systems with Wind Farms
(National Institute of Technology Karnataka, Surathkal, 2024) Rashmi; Gaonkar, Dattatraya N.
A global trend in the growth of power systems is to build interconnections with the aim of achieving technical, economical and environmental benefits.The interconnections facilitate exchange of power between different regions or countries improving the utilization, flexibility, power quality, efficiency of transmission and emergency support. High Voltage Direct Current (HVDC) systems emerge as a compelling and efficient solution for long-distance power transmission, asynchronous system interconnection, and renewable energy integration. As offshore wind generation is exploited at increasing distances from shore, HVDC stands out as the preferred transmission method. Offshore wind farms equipped with Direct Drive Permanent Magnet Synchronous Generators (DD-PMSG) are drawing increased attention due to their advantage over other variable speed technologies. Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) links are considered the most suitable option for transferring power to the onshore system. The rapid development of VSC-HVDC based offshore wind farms have highlighted the need for these stations to synchronise with the grid independently and provide inertial support, especially as grid strength declines, rendering phase-locked loops (PLLs) ineffective. In this context, the research work deals with the systematic analysis of Line Commutated Converter based High Voltage Direct Current (LCCHVDC) links, Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) links and integration of VSC-HVDC based offshore wind farms into multi-machine systems. Specifically, the study presents a performance analysis of synchronous and asynchronous multi-machine systems using tie-lines as LCC-HVDC links. Detailed inferences are drawn for the systems subjected to various dynamic events in comparison to systems with Thyristor Controlled Series Capacitor (TCSC) lines. The effect of variation of synchronous tie-line power levels on the modal behaviour is investigated. The asynchronous system modes are analysed with reference to the modes of its synchronous counterparts. The impact of VSC-HVDC active and reactive power controls on frequency controllers is assessed. The effect of feedforward and feedback active power loops are examined through bandwidth analysis. The influence of reactive power controllerson the performance of frequency controllers is also studied. Additionally, a simplified model of VSC-HVDC link is proposed that can be efficiently used for analysis of links embedded in large AC systems. This model offers lesser modelling complexity and computation time, enhancing efficiency in analysis. Following the above analysis, the integration of VSC-HVDC connected DDPMSG based offshore wind farms into multi-machine systems is explored. A novel approach for power flow and initial condition calculations is proposed to facilitate dynamic analysis of the system. For three cases of the most commonly specified quantities of the wind farm, efficient methods have been described. This approach enables the user to build the model in any basic graphical dynamic modeller and numerical computational software without requiring power system toolboxes or electromagnetic transient packages. Case studies and simulations are conducted to verify the proposed technique. The work further presents a novel approach for grid synchronisation and inertial support from VSC-HVDC based offshore wind farms. The DC capacitor dynamics are utilised to imitate the rotor dynamics of a synchronous generator for synchronisation, while inertia support is derived from the DC capacitor energy and the hidden inertia of the offshore wind farm. A time constant based approach employing two distinct DC voltage tolerance bands for the control is proposed. This leads to improved inertial response and a very easy selectionof controller parameters. The effectiveness of the strategy has been proved in high impedance and low inertia systems. MATLAB/SIMULINK has been used for the study.
Performance Investigation of Electric Vehicle Charging in a Bipolar DC Microgrid
(National Institute of Technology Karnataka, Surathkal, 2024) S. Nisha, K.; Gaonkar, Dattatraya N.
Transportation electrification and charging infrastructure in India has to gain momentum in accordance to development of electric vehicle technology. Charging of electric vehicles is going to be a major electrical load in the near future, as more and more population shift to electric automotives from internal combusted engine-powered vehicles. Integration of electric vehicle charging stations might even burden the existing grid to a point of collapse or grid failure. Thus, an alternate grid structure is a necessity in the near-futures, for the powering the EV loads. Emergence of distributed energy sources and compatible technologies makes dc microgrids more popular compared to ac grids. Besides electric vehicle loads is primarily a battery which is dc in nature. Setting up charging stations integrated to microgrids can avoid the overburdening of the primary utility grid, by benefiting the distributed energy resources. The bipolar DC microgrid is a far better microgrid structure than the unipolar microgrid structure in many aspects like reliability, flexibility, and controllability. It can provide multiple voltage level interfaces according to the load demands, which is very apt for different charging levels of electric vehicles. Thus bipolar dc microgrid is the best answer we can put forward for the new age power grid. Establishing charging infrastructure interfaced with bipolar DC microgrids along the roads and highways is the most realistic and feasible solution to avoid the overburdening of the existing power system. Operation of multiple sources and loads connected to bipolar DC microgrid will affect voltage regulation, and overall stable operation of the grid. Along with this, intermittent nature of renewable energy resources and unpredictable charging and discharging behaviour of EVs aggravate the power imbalance between two poles of dc microgrid. This leads to voltage unbalance issues in bipolar dc microgrid. This thesis proposes bipolar converter configurations and fast acting nonlinear control strategies which can address voltage balancing and power sharing issues efficiently as well as integrate electric vehicle charging stations to bipolar dc grid. A bipolar dc grid in this research work consists of photovoltaic power generation, DC loads and a battery system as auxiliary energy storage. Three level boost converter derived from neutral point clamped converter configuration is used for connecting PV systems to bipolar dc grid. Bipolar converter based on three level buck boost converter is used to connect battery energy storage system to microgrid. This bidirectional converter is operated such that auxiliary battery storage bridges the power gap between load demand power and generated power. Discrete state space modelling of the three level converters is done and model predictive control is developed, which is fast acting and more robust than PI control. With model predictive control, voltage regulation, pole capacitance voltage balancing, MPPT tracking and overall stable operation of the bipolar dc microgrid is ensured. Simulation of the proposed model predictive control with three level converters is done in Typhoon Schematic Editor and Simulink. Hardware in loop testing of the model predictive control of the bipolar dc microgrid is done with Typhoon HIL 402 and validated in virtual and real time hardware in loop environment. EV load profile is developed for a cluster of vehicles considering different driving profiles and different vehicle dynamics. V2G and G2V regulation and control is implemented in integrating this EV load profile to bipolar dc grid. Multi-port three level converter is proposed for connecting electric vehicle charging stations. An overall decentralized model predictive control of multi-node bipolar dc grid with EV load profile, PV generation, BESS and dc loads is implemented effectively and analysed under dynamic grid conditions.