Browsing by Author "Arachchige, LNW"

Now showing 1 - 10 of 10

item: Conference-Full-text
Converting a commercial-consumer-fed, ring distribution system into a diesel-solar hybrid microgrid: technical feasibility
(IEEE, 2022-07) Herath, HDBP; Arachchige, LNW; De Silva, PSN; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Complex distribution networks like ring or meshed networks are applied for commercial and industrial cities demanding reliable power supply. Diesel generators are connected to the network to maintain system reliability under emergency states. With increasing penetration of non-dispatchable, rooftop solar-PV, proper planning is required to maintain system stability and reliability. Commercial and industrial cities do not follow the conventional diurnal load patterns, but presents load patterns similar to the diurnal generation curve of solar-PV. Thus, by introducing solar-PV, required diesel generation capacity can be reduced. Also, the system reliability and stability can be improved if the system is operated as a microgrid. The ability of forming ring-radial connected hybrid-microgrid based on an existing network for a commercial city with peak day-time loading is evaluated. Small-signal stability analysis reveals that, even with 100% solar-PV, the islanded microgrid in normal state is stable under different diesel generation integration topologies tested. The system becomes unstable due to small perturbations under the N-l emergency operation in some topologies. This study allowed identification of the proper diesel generation integration topology for the proposed microgrid.
item: Thesis-Full-text
Designing of a grid tie inverter for commercial and household solar power installations based on a solid-state transformer topology
Peiris, PSA; Arachchige, LNW; Wijekoon, HM
Solar PV installations have gained a rapid popularity in Sri Lanka due to the reduction of PV panel costs and government incentives to promote renewable energy. The presence of these PV inverters has introduced power quality problems at the LV grid, mainly due to the injection of harmonics and DC currents. The objective of this thesis is to study the power quality issues of the existing transformerless inverters and propose a solar PV inverter configuration based on a solid-state transformer (SST) topology. Upon recognizing the drawbacks of the existing configurations, three inverter configurations were developed based on the dual active bridge (DAB) and Tri active bridge (TAB) configurations utilized in the solid-state transformer. Two configurations for the DAB based inverter are presented. Mathematical modelling of the TAB converter is presented with its associated converter currents and voltages. Based on the mathematical model, controllers were derived to maintain the DC bus voltages and the power flow of the TAB. Output filter designs, MPPT algorithm selection, power flow controllers and PV array selection procedures are presented along with the inverter configurations. The developed systems were simulated and compared with the transformerless system in the MATLAB Simulink platform to assess their improvements. The load side harmonic isolation capabilities and the fault current limiting capabilities of the DAB and TAB based PV inverter systems are presented. The TAB and transformerless systems were also simulated with the presence of grid voltage harmonics. In all the cases tested, the TAB based system provides excellent power quality and fault current limiting capabilities over the transformerless system.
item: Conference-Full-text
Development of a software tool for power flow analysis in a distributed generation integrated radial distribution system
(Institute of Electrical and Electronics Engineers, Inc., 2021-09) Guruge, P; Kodikara, A; Karunasena, P; Arachchige, LNW; Abeykoon, AMHS; Velmanickam, L
Distribution system power flow analysis has significant differences when compared with that of transmission systems owing to their special topological properties. Hence, application of conventional power flow methods on illconditioned distribution systems brings out unsatisfactory results. Integration of distributed generation has caused the distribution system to become no longer passive in nature, highlighting the importance of more precise algorithms for power flow analysis. Solving power flow problems, which are mostly based on solving systems of non-linear algebraic equations can be efficiently done using software tools. However, most of the available software tools are focused on transmission systems and are very expensive. This study focuses on coming up with a software tool to solve power flow problems in distributed generation integrated radial distribution systems, which can be used as a teaching tool at universities. The proposed algorithm is based on the Forward Backward Sweep Method, and attempts have been made to model each distribution system component in a way that reflects the system parameters reasonably. Algorithm was tested on standard IEEE 4 Bus system, IEEE 13 Bus system and IEEE 15 Bus system, and the results were analyzed to assess the validity of the proposed algorithm.
item: Thesis-Abstract
Effect of embedded generators on Sri Lanka power system frequency fluctuations
Arachchige, LNW; Nanayakkara, DPN
The purpose of this research was to review the current utility operating methods and associated technical issues, basically on frequency stability in Sri Lanka when considering embedded generation connected to distribution network, and to examine the prospects for future active operation and control of the network. A comprehensive software based study was done which allowed identifying some prospective modifications for a more active approach to the operation of the power system to accommodate the expected amount of embedded generation that is likely to be connected in the coming decade in order to meet the government targets. Different loading conditions based on the load curve was assed and technical issues on protection, basically Rate of Change of Frequency (ROCOF) protection and load shedding were covered in detail, and a new load shedding scheme was proposed. Guidelines were suggested to the future modifications and control of the network. These will allow the embedded generation developers and the Ceylon Electricity Board (CEB) to maximize the potential of embedded generation and improve the utilization of their network.
item: Article-Full-text
Implementation, comparison and application of an average simulation model of a wind turbine driven doubly fed induction generator
(MDPI, 2017) Arachchige, LNW; Rajapakse, AD; Muthumuni, D
Wind turbine driven doubly-fed induction generators (DFIGs) are widely used in the wind power industry. With the increasing penetration of wind farms, analysis of their effect on power systems has become a critical requirement. This paper presents the modeling of wind turbine driven DFIGs using the conventional vector controls in a detailed model of a DFIG that represents power electronics (PE) converters with device level models and proposes an average model eliminating the PE converters. The PSCAD/EMTDC™ (4.6) electromagnetic transient simulation software is used to develop the detailed and the proposing average model of a DFIG. The comparison of the two models reveals that the designed average DFIG model is adequate for simulating and analyzing most of the transient conditions.
item: Thesis-Abstract
Optimal sizing of the energy storage system through cost minimization in a microgrid using demand response techniques
(2023) Ariyarathne, RMAS; Arachchige, LNW
Employment of Energy Storage Systems (ESS) in microgrids has become important as it enhances the overall performance of microgrids. With the improvement in the technologies associated with power system optimization, developing an exact model to identify the optimal size of ESS, which brings the maximum benefits to the microgrid with the least cost has become a major research area. In this research, the optimization of ESS in a selected microgrid is carried out under the implementation of a Demand Response (DR) program. The main aim of this research is to determine the optimal size of ESS that minimizes the investment cost and maintenance cost of ESS, together with the operating cost within microgrid. Due to the uncertain nature of the load and PV generation, a stochastic model was employed to predict those parameters accurately. Dynamic Programming (DP) is used to model the optimization problem in GAMS optimization software. Two cases were studied to evaluate the effectiveness of the proposed methodology, and the results highlight that the implementation of Demand Response Program leads to a curtailment in the size of Energy Storage System and a reasonable reduction in the total cost in the microgrid.
item: Thesis-Full-text
Techno-Economic Feasibility Of 400kv For The 2032 Transmission System Of Sri Lanka
Alahendra, GB; Arachchige, LNW; Wijekoon, HM
Electricity is a basic need for the economic growth of any country. Therefore, the electricity demand grows at a higher rate with the rapid development of the economy. To meet the increasing demand of electricity, addition of new generation capacity into the system is required.However, with new generation additions, there should be a way to transmit bulk power to load centers. This transfer of power is done through the transmission network. Transmission system of Sri Lanka mainly operatesat 220 kV and 132 kV voltage levels and it interconnects the grid substations (GS) and power stations (PS). Together with the increase of electricity demand and bulk power generation, there is a point at which introduction of new higher voltage level is required for reliable, efficient and better quality of supply. However, it has to be technically feasible and economically justifiable. This study focuses on the major bulk power transmission from Sampur, Ambalangoda and Hambanthota generation stations of Sri Lanka to load centers. Two power system models for each 220kV and 400kV voltage level options were developed for the years 2025 and 2032. These models were analyzed for voltage stability using PV and QV curves in order to find the technical feasibility between the two options. Then the economic analysis between the two options was performed in order to assess the economic feasibility of the two options.Technical feasibility and economic justification of introducing a higher voltage than that of existing voltage to transmit bulk power to load centers from bulk power generating stations in Sri Lanka is discussed in detail in this research.
item: Conference-Abstract
Under-frequency load shedding for power systems with high variability and uncertainty
(2014-06-20) Bambaravanage, T; Kumarawadu, S; Rodrigo, A; Arachchige, LNW
Emergency load shedding for preventing frequency degradation is an established practice all over the world. The objective of load shedding is to balance load and generation. This paper presents a methodology to develop a reliable load shedding scheme, to prevent black-outs while maintaining stability in power systems with high variability and uncertainty under any abnormal condition. The technique proposes the sequence and conditions of applications of different load shedding schemes and islanding strategies. The effectiveness of the developed scheme was investigated by simulating different abnormal conditions in the power system of Sri Lanka.
item: Conference-Full-text
Under-frequency load shedding for power systems with high variability and uncertainty
(2015-07-02) Bambaravanage, T; Kumarawadu, S; Rodrigo, A; Arachchige, LNW
Emergency load shedding for preventing frequency degradation is an established practice all over the world. The objective of load shedding is to balance load and generation. This paper presents a methodology to develop a reliable load shedding scheme, to prevent black-outs while maintaining stability in power systems with high variability and uncertainty under any abnormal condition. The technique proposes the sequence and conditions of applications of different load shedding schemes and islanding strategies. The effectiveness of the developed scheme was investigated by simulating different abnormal conditions in the power system of Sri Lanka.
item: Conference-Full-text
Voltage control of three phase distribution systems with minimum cost
(IEEE, 2021-07) Manamperi, DI; Dissawa, LH; Arachchige, LNW; Binduhewa, P; Ekanayake, JB; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Prevention of voltage rise under minimum cost in distribution networks with high PV penetration is considered in this study. On load tap changing (OLTC) transformer and PV inverters are used as controllable devices. The actual cost minimization of transformer tap change, inverter curtailment and line losses is considered as the objective of the optimization problem. Sequential use of mixed integer second order cone (MISOCP) program is used as the optimization technique. Simulations results demonstrate the capability of voltage regulation under minimum cost. Exactness of the generated solutions are validated after comparison with load flow.