Electrical Engineering
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Item TRANSIENT STABILITY ANALYSIS OFAN INTERCONNECTED ELECTRICAL POWER SYSTEM(I.O.E. Pulchowk Campus, 2023-04) Poudyal, Deepak; Jha, Raushan KumarSince solar power systems are connected to the grid using technologies other than those used by traditional power systems, the increased penetration of solar energy into the traditional power grid may modify certain of its transitory features. Particularly, the increased use of non-synchronous generators has an impact on the Critical Clearing Time (CCT), which is crucial for protective system performance during turbulent periods. In a typical IEEE 9 bus test system, this work examines the transient stability analysis of a power system and the effects of photovoltaic (PV) penetration on it. The simulation software ETAP is used to prepare the Simulink model for the transient stability of the IEEE 9 bus test system. The study takes into account three-phase faults, and several simulations are used to examine the stability of the rotor angle. Critical clearing time is used to compare the transient stability in various scenarios, such as with and without PV in the system, and is used as an index to examine the transient stability analysis of the IEEE 9 bus test system for base case. It has been discovered that transient stability depends on the fault's duration, position, and power. While it has improved in some places, the integration of PV into the system has decreased the transient stability of the power supply at important spots.Item “SELECTIVE HARMONIC ELIMINATION”(I.O.E. Pulchowk Campus, 2023-04) Kunwar, Jibalal; Paudel, Prakash; K.C., Ramesh; Bista, SanilSelective Harmonic Elimination (SHE) is a widely used technique in power electronic converters to mitigate the detrimental effects of harmonics on system performance. Harmonics, which are undesired sinusoidal components occurring at frequencies that are multiples of the fundamental frequency, can lead to waveform distortion, increased losses, and interference with other electronic devices. The SHE technique selectively eliminates specific harmonics from the output waveform by precisely controlling the switching instants of the converter. This research project focuses on investigating the theory and implementation of Selective Harmonic Elimination for square wave inverters, which commonly produce harmonically rich waveforms due to the abrupt transitions in the output voltage. The primary objective of this study is to design a selective harmonic elimination pulse width modulation (SHE PWM) controller for square wave inverters to reduce the Total Harmonic Distortion (THD) present in the output waveform. The research project aims to develop an effective SHE algorithm capable of selectively eliminating specific harmonics while preserving the desired characteristics of the output waveform.Item “DESIGN AND FABRICATION OF SOLID-STATE ON-LOAD TAP CHANGER”(I.O.E. Pulchowk Campus, 2023-04) Neupane, Kismat; Niraula, Kshitij; Chaudary, Mahesh; Ray, NikeshIn the recent time, the continuous, uninterrupted and fast power supply along with high efficiency is one of the major concerns in the field of power system. It is necessary that our system should react quick to increase and decrease in heavy as well as light load. The on-load tap changers have become one of the important parts of transformer in order to regulate the constant output voltage without disconnecting the load. The purpose of this project is to design the most convenient type of tap-changing system that omits all the disadvantage of the present type of tap changing. It focuses on how current tap changing system is working, what are the problems associated with it and hence how can we replace them by using modern tools, devices, systems and methods. Earlier mechanical type on-load tap changers were in use which had major shortcomings like arcing, slow response time, high maintenance and service costs. And these get even worse in the case distribution transformers which are manually operated that too after disconnection of load and hence do not provide dynamic control over output voltage and require constant human intervention. Due to these flaws of the mechanical type, solid-state (electronic) tap changers were introduced.Item ENHANCEMENT OF FAULT RIDE THROUGH CAPACITY OF GRID CONNECTED INVERTER(I.O.E. Pulchowk Campus, 2023-04) Yadav, Barma; Paudel, Bishnu; Pokharel, Kajal; Mahato, Rahul KumarUnder the demands of contemporary grid code (GC), the solar PV system should stay attached to the grid for a certain time period depending on the voltage sag level under the fault condition. The voltage of the point of common coupling (PCC) is the same when the fault appears on the grid side due to compensation of voltage by the grid connected system. But the output voltage of inverter is very low when fault occurs in the inverter side resulting in a very high DC connection voltage and very high current through the inverter for the power balance. This high voltage of the intermediate circuit can damage the DC link capacitor and high current during the transient fault may damage the inverter. Moreover, the deflection of the voltage will cause the PV plant to be disconnected from the network based on the modern GCs. But, due to on-growing demand of consumers, it is required to connect the PV system to grid even during faulty condition. This study proposes a DC Braking chopper approach for the two-stage grid-integrated solar PV system to enhance fault ride through (FRT) capability. The proposed DC Braking control approach consists of a resistor in series with IGBT which absorbs the excess energy in the DC link capacitor during the fault, which will regulate the DC-link overvoltage where required PWM signal for IGBT used in DC braking chopper is generated by the principle of power balance between DC side and AC side.Item ACTIVE CELL BALANCING APPROACH FOR EFFICIENT BATTERY MANAGEMENT SYSTEM(I.O.E. Pulchowk Campus, 2023-06) Sharma, Aakriti; Adhikari, Anusha; Adhikari, Bibek; Pandey, PratikThis project proposes a novel approach for improving the efficiency of battery management systems through active cell balancing using the Kalman filter algorithm and build a hardware prototype model for testing and validation of the results. The goal of this project is to develop a system that can extend the lifespan of batteries by ensuring that each cell is charged and discharged evenly. The proposed system includes an active balancing circuit that uses the Kalman filter algorithm to estimate the state of each battery cell and determine the optimal charging and discharging currents. This approach is designed to reduce the energy loss associated with passive balancing circuits, which can be a significant source of inefficiency in battery management systems. The project includes simulation studies using MATLAB and Simulink and experimental results to demonstrate the effectiveness of the proposed system. The simulation studies will be conducted to optimize the design of active balancing circuit and Kalman filter. The experimental results confirm the effectiveness of the Kalman filter algorithm in estimating the state of each battery cell and optimizing the charging and discharging currents. The experimental studies will involve testing hardware prototype model using actual battery cells and the developed active balancing system.Item COMPENSATION FOR REACTIVE POWER AND HARMONIC CURRENTS DRAWN BY NON-LINEAR LOAD IN PV-MICRO HYDRO GRID(I.O.E. Pulchowk Campus, 2023-04) Thapa, Ajay; Karmacharya, Raisha; Nepal, Raj Krishna; Khatiwada, SanketThis project proposes a method to improve the power quality of a PV micro hydro grid by utilizing instant PQ theory and hysteresis current control band logic. The main goal is to mitigate harmonics and ensure reliable utility power supply. This is achieved through the use of a shunt active power filter, which acts as a current source and cancels out harmonics by injecting equal and opposite harmonic components at the grid connection point. The proposed system includes a shunt active power filter with an inverter that employs the instantaneous PQ theory algorithm to generate reference current. The hysteresis band current control logic utilizes the reference current in the a-b-c frame to generate appropriate gate signals for the inverter, ensuring that the current drawn from the inverter tracks the reference currents within a specified band, thereby compensating for the non-linear load. The MATLAB-Simulink Toolbox is used to simulate the shunt active power filter in order to demonstrate its efficiency and adaptability. The simulation considers two different types of loads to validate the effectiveness of the proposed scheme. The simulation results are analyzed and evaluated. Overall, the project aims to design a system that can compensate for reactive power and harmonic current consumed by the load. By ensuring nearly sinusoidal current in proportion to the active power, the system aims to improve the power quality of the PV micro hydro grid.Item MODELING OF GRID TIED PV INVERTER TO IMPROVE ITS PERFORMANCE DURING UNBALANCE LOAD AND UNBALANCE FAULT(I.O.E. Pulchowk Campus, 2023-04) Dahal, Aashish; Khanal, Bibek; Bhattarai, Kulchandra; Shrestha, LenishWith the demand of alternative source of energy, there is an increasing trend in solar power plants, as it is abundant, clean and has significantly reduced the reliance on conventional energy sources. Integrating solar through inverter brings about various challenges in the microgrids and the inverter itself. This project aims the study of problems in the operation of inverter during unbalance load and unbalance fault condition along with the possible control measures to mitigate those problems to ensure the safe and reliable operation of the inverter. A grid connected PV inverter is modeled using hysteresis band controller and implementing the MPPT of the PV system with the buck boost converter. During unbalance load and unbalance fault condition, the negative and zero sequence components of current exists. All the zero-sequence component of current is delivered by the grid. The negative sequence component of current also flows through the inverter resulting in high value of current and loss of stability. Also, the voltage across the dc link capacitor increases during voltage dip. The high value of current flowing through the inverter and high voltage across dc link capacitor may damages the inverter and capacitor respectively.Item “MULTI BATTERY BLOCK MODULE POWER CONVERTER FOR ELECTRIC VEHICLE DRIVEN BY SWITCHED RELUCTANCE MOTOR”(I.O.E. Pulchowk Campus, 2023-03) SONAR, NILESH SAH; KARKI, SITARAM; POKHAREL, SWASTIKA; GHIMIRE, VIBEKThis project proposes an innovative approach to control and regenerate energy from a switched reluctance motor (SRM) for electric vehicles using a multi-battery system. By adopting this configuration, the proposed system overcomes the limitations of a single battery pack and maximizes the potential of the SRM. The control system implemented in this project utilizes a proportional-integral (PI) controller, which is carefully optimized to ensure efficient operation and minimize losses. The PI controller plays a crucial role in maintaining the desired performance of the SRM while achieving optimal energy regeneration. Through simulation on a 75 kW SRM, the results of this project exhibit significant enhancements in performance compared to traditional control methods. Notably, an impressive 26% of energy regeneration is achieved, which greatly contributes to the overall efficiency of the system.Item DESIGN AND HARDWARE IMPLEMENTATION OF MULTILEVEL INVERTER(I.O.E. Pulchowk Campus, 2023-04) Sah, Bharat Kumar; Thakur, Chandan; Goswami, Sagar; Kadel, UjjwalAn inverter is utilized to transform a DC source into an AC source using power electronic components. It can be achieved using two types of inverters, one is two level inverter and another is multilevel inverter (MLI). MLI has been implemented in various applications, such as motor drives, power conditioning devices, renewable energy generation and distribution. PWM inverters can simultaneously control output voltage, frequency and it can reduce the THD content in output waveform. This project aims in the study of different MLI topologies, primarily focused in the study of Cascaded H bridge (CHB) and Switched Capacitor MLI (SCMLI). Several multilevel topologies have been developed, but as the output voltage level increases, it also increases the number of switches, switching stresses, losses and voltage unbalancing across the capacitors, etc. CHBMLI is more efficient compare to the other topologies of multilevel inverter but not as efficient as Switched Capacitor MLI. SCMLIs are the most widely used because of self-voltage balancing and voltage boosting over conventional ones with reduced number of DC sources.Item ANALYSIS OF THE IMPACT OF EV PENETRATION ON PROTECTION COORDINATION(I.O.E. Pulchowk Campus, 2023-04) Yadav, Prem Kumar; Yadav, Ram Pukar; Sah, Sachidanand; Jha, SashishThe global electric vehicle (EV) market has witnessed significant growth in recent years, driven by concerns over climate change, advances in battery technology, and supportive government policies. To address environmental pollution and the increasing energy consumption associated with conventional transportation systems, the adoption of EVs has emerged as a more sustainable alternative. However, the rapid increase in EV charging loads has raised significant operational challenges for power grids. This research project focuses on the impact of EV integration on relay and protection coordination in distribution systems. Relay and protection coordination plays a crucial role in ensuring the safe and reliable operation of distribution systems by detecting abnormal conditions, such as faults or abnormal load conditions, and isolating the affected section to prevent further damage or outages. With the proliferation of EVs, the increased charging load introduces harmonic currents that can disrupt the operational parameters of the power grid. This study utilizes the IEEE standard 33 bus distribution system as a testbed to evaluate protection coordination using genetic optimization techniques. By adding EV chargers at various nodes of the distribution system, the project assesses the time required for circuit breakers to trip in the event of a fault, evaluating the effectiveness of protection coordination techniques in the presence of EVs. The findings reveal that while the replacement of standard loads with EV chargers leads to a slight increase in the net RMS value of current and introduces harmonic currents, the sequence of relay operation remains unaltered. However, the relay operation time is affected, and in scenarios with bulk penetration of EV chargers, the increased harmonic current can cause overloading and other faults, resulting in relay trips. To ensure the proper protection of the system, it is recommended to increase the pickup current for the relays. By adjusting the pickup current level, the relays will trip at higher current levels, mitigating false tripping caused by harmonic currents from EV chargers. The study emphasizes that meticulous design and planning are essential to maintain the reliability and protection of power distribution systems when integrating EV chargers.Item HOURLY LOAD SHIFTING APPROACH FOR DEMAND SIDE MANAGEMENT(I.O.E. Pulchowk Campus, 2023-04) CHAUDHARY, DINESH; ARYAL, PRATIBHA; CHAUDHARY, SUSHIL; GIRI, UJWALThe generation capacity of power stations is limited, and electricity consumption varies throughout the day, with high demand during peak hours and lower demand during offpeak hours. Balancing the supply of electrical power according to the load is essential, and simply increasing the number of generation units is not the sole solution to meet the increasing demand. Demand Side Management (DSM) offers a solution by optimizing load patterns instead of solely relying on increasing power output. DSM enables customers to save on energy bills while ensuring network operators maintain network reliability and avoid unexpected surges in demand that can lead to power outages. By scheduling usage, DSM allows for better load balancing. This report proposes a load shifting-based demand side management strategy to reduce peak hour demand. The objective is to minimize peak demand through an optimization problem formulated in the MATLAB R2021a environment. The proposed strategy seeks to find an optimal solution that maximizes efficiency.Item SMART EV CHARGER WITH REACTIVE POWER COMPENSATION(I.O.E. Pulchowk Campus, 2023-06) Ghimire, Ankit; Dhungel, Ashish; Thapa, Deepak; Bhandari, NirajanThe voltage drop is a serious issue that the grid is facing at present due to the penetration of a large number of EVs. For this at present STATCOMs and Capacitor banks are used, however STATCOMs are expensive and Capacitor Banks have less reliability. In this situation we came up with an idea to embed the functions of such compensating devices into the charger itself in order to increase the system reliability and reduce the use of such expensive devices. This paper illustrates the overall procedure of the prototype design of the system and an EV charger that regulates the voltage at the user end. As our final year project, we sought to develop a smart EV charger that compensates for the reactive power in the grid and maintains the voltage at the user end while charging the vehicle battery simultaneously. The project was carried out first in simulation (MATLAB) and then proceeded with hardware implementation right from the scratch. At first, we simulated the design in a Three phase system and observed the result in MATLAB Simulink. The charger works as a boost rectifier thus we were able to charge a 60 KW charger at unity power factor. While charging, the node voltage was dropped significantly low below the standard limit. Thus, in order to regulate the voltage at the node of connection. We supplied the reactive power to the grid through the charger.