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At household level, the development of appliances has recently increased the presence of internal DC links. This, combined with the diffusion of the smart full-electric house concept including embedded generators and storage systems (typically operating in DC), could modify the present AC paradigm towards the partial use of DC distribution schemes. The end-user system architecture based on the solid...
The problem of regulating voltages within the required limits is complicated by the fact that power system supplies power to a vast number of loads and is fed from many generating units. As loads vary, reactive power requirements of the transmission system vary. Moreover, voltage magnitude is relatively less sensitive to active power compared to reactive power due to high X/R ratio of transmission...
Voltage deviations occur frequently in power systems. If the violation at some buses falls outside the prescribed range, it will be necessary to correct the problem by controlling reactive power resources. In this paper, an optimal algorithm is proposed to solve this problem by identifying the voltage buses, that will have a maximum effect on the affected buses, and setting their new set-points. This...
Photovoltaic generators can provide several benefits for distribution networks, such as power loss reduction, and improvements in voltage level. However, high penetration of these generators can cause voltage rise problems in the distribution network. In this way, voltage control strategies are necessary so that the voltage levels are within the range of operation for any load and generation conditions...
The control strategies of micro grid is an important topic for micro grid. With the development of DC micro grid, the control strategies of DC micro grid is drawing more and more attention. Nowadays, the most widely used control strategy of DC micro grid is droop control. All the distributed generators and energy storage systems share loads through different droop coefficients in droop control. This...
DC distribution systems (DCDS) connect local generators and loads directly. By avoiding unnecessary losses in AC-DC conversion, DCDS offers higher energy efficiency. Since different parties in a DCDS may have conflicting goals, matching between power supply and demand should be done with carefully designed allocation rules and monetary transfers, such that no one prefers to act otherwise than the...
This paper aims to propose a secondary control algorithm based on Fuzzy Logic to adjust frequency and voltage in islanded microgrids. It is well-known, that, when a microgrid changes its operation from grid-connected to islanded mode, the time domain variability of the loads will change the frequency and voltage profiles of the system. In this sense, the operation of the system might become unsafe...
Domestic installations traditionally were believed to be resistive in nature and did not affect power factor much, if at all. With increasing affordability of air-conditioners, and replacement of electrical geysers with heat pumps, loads are becoming more inductive. Small-scale renewable energy generation through e.g. solar photo-voltaic (PV) panels are becoming more affordable and as such are connected...
The lack of operational flexibility in the transmission grid to react to unexpected system failures caused by the shutdown of conventional power plants requires future active distribution networks to participate in transmission system support, e.g., providing ancillary services. Thus, the need for adequate control strategies to integrate distributions networks in the operation and control systems...
In this study, in order to reduce the abnormal voltage drop or rise in the distribution systems with distributed generators, we consider a multi-objective function to be optimized in such a way that the voltage profile is enhanced while the total active power loss in the network is minimized under some operational constraints. Capacitors and static VAR compensators are also coordinated with the distributed...
This paper demonstrates the already established fact that by using Distributed Generation (DG), voltage profile of a distribution system can be improved. N-R method is used for load flow analysis. A standard IEEE 14-bus power system is used. To reduce losses three optimization techniques i.e. PSO(Particle Swarm Optimization), GSA(Gravitational Search Algorithm) and hybrid PSOGSA is applied to the...
Constraint management is one of the critical tasks for ensuring secure operation of power supply systems and is generally formulated and solved as an optimal power flow (OPF) problem with generation scheduling and voltage set point controls. In case of severe contingencies, conventional OPF methods may fail to converge, i.e. find solution satisfying all constraints. In such cases, network operators/planners...
The amount of photovoltaic (PV) generation that can be hosted by existing radial distribution feeders is inherently limited by system constraints and operating conditions. This paper discusses an analysis to determine the photovoltaic hosting capacity of an existing radial distribution feeder. This analysis also visualizes the location-dependence of hosting capacity, and tests the effectiveness of...
This paper proposes a new approach for finding the minimum number of post-contingency corrections to relieve overload. The security-constrained optimal power flow (SCOPF) problem with AC power flow constraints can be formulated as mixed integer nonlinear programming (MINLP), which is an NP-hard problem. A two-stage approach—screening and detailed analysis—is utilized to solve the non-convex MINLP...
The modular multilevel converter (MMC) with cascaded full bridge cells is available for an AC/AC transmission system without transformers in high voltage line. When it is interconnected with power line, it is possible to control the active power flow in order to supply the power to the power line. This research applied the MMC to grid connection system of distributed generator for single phase AC/AC...
The recent development of dispersed generation leads to fact that distribution grids have to deal with the bidirectional power flow which may cause voltage rise above permissible level. Currently used voltage regulation scheme cannot completely and successfully cope with this problem. As a result of the further increasing penetration of distributed generation, the new voltage regulation system will...
The demand of electricity is soaring rapidly. Distributed generation (DG) is one of the most suitable alternatives to fulfill this swelling demand of energy. DG is a small scale generation which is directly installed in the distribution network or at load centre. Optimal allocation of DG is a vital factor in improving the voltage profile of the system and in reduction of total power losses. DG size...
Reduction of generation cost and transmission losses is one of the most important issues of today's power systems. In this paper, a multi- objective optimal power flow using a biologically inspired, Krill herd (KH) Search Algorithm has been proposed. Unified Power Flow Controller (UPFC) is a multilateral device in the Flexible Alternating Current Transmission System (FACTS) family which has the capability...
The integration of a high penetration of intermittent distributed generation (DG) poses challenges to the planning and operation of the grid. In order to increase the acceptable capacity of DG, this paper researches on the sizing of DG based on active operation. After the analysis of several scenarios, a technical framework of secondary voltage control system is set up. It coordinates day-ahead control...
This paper analyses the 11 kV Medium Voltage (MV) networks using real network and load data. High penetration Photovoltaic (PV) connected to a MV feeder is modeled using RETScreen to estimate the output power based on meteorological and geographical data. Simulations are run across 24 hour period to see the voltage fluctuations, active and reactive power behavior, load profile, power loss and energy...
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