بایگانی برچسب برای: Distributed generation

Optimal Renewable Resources Mix for Distribution[taliem.ir]

Optimal Renewable Resources Mix for Distribution System Energy Loss Minimization

It is widely accepted that renewable energy sources are the key to a sustainable energy supply infrastructure since they are both inexhaustible and nonpolluting. A number of renewable energy technologies are now commercially available, the most notable being wind power, photovoltaic, solar thermal systems, biomass, and various forms of hydraulic power. In this paper, a methodology has been proposed for optimally allocating different types of renewable distributed generation (DG) units in the distribution system so as to minimize annual energy loss .The methodology is based on generating a probabilistic generation-load model that combines all possible operating conditions of the renewable DG units with their probabilities, hence accommodating this model in a deterministic planning problem. The planning problem is formulated as mixed integer nonlinear programming (MINLP), with an objective function for minimizing the system’s annual energy losses. The constraints include the voltage limits, the feeders’ capacity, the maximum penetration limit, and the discrete size of the available DG units. This proposed technique has been applied to a typical rural distribution system with different scenarios, including all possible combinations of the renewable DG units. The results show that a significant reduction in annual energy losses is achieved for all the proposed scenarios.
A Novel Protective Scheme to Protect Small-Scale[taliem.ir]

A Novel Protective Scheme to Protect Small-Scale Synchronous Generators Against Transient Instability

Installation of small generators in distribution networks has been increased recently due to its various benefits. One of the important issues related to these distributed generators is the effect of system faults on their transient stability. Due to the low inertia constant of the small-scale generators and the slow operation of the distribution networks’ protective relays, transient instability is quite probable for these generators. In this paper, the dynamic behavior of small-scale synchronous generators to the system faults and its sensitivity to the system parameters are investigated. Then, a practical protective method using theexisting overcurrent and undervoltage relays is proposed, and its advantages and disadvantages are pointed out. Next, based on the obtained information from sensitivity analysis, a novel protective relay is proposed to protect the generators against instability. The proposed relay uses a generator active power to determine the appropriate time to disconnect the generator. Simulation results confirm the secure operation and robustness of the proposed relay against system transients. In addition, the proposed algorithm complies with the generator fault-ride-through requirements.
A New Control Strategy for a Multi-Bus MV[taliem.ir]

A New Control Strategy for a Multi-Bus MV Microgrid Under Unbalanced Conditions

This paper proposes a new control strategy for the islanded operation of a multi-bus medium voltage (MV) microgrid. The microgrid consists of several dispatchable electronically-coupled distributed generation (DG) units. Each DG unit supplies a local load which can be unbalanced due to the inclusion of singlephase loads. The proposed control strategy of each DG comprises a proportional resonance (PR) controller with an adjustable resonance frequency, a droop control strategy, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and share the average power components among the DG units. The NSIC is used to effectively compensate the negative- sequence currents of the unbalanced loads and to improve the performance of the overall microgrid system. Moreover, the NSIC minimizes the negative-sequence currents in the MV lines and thus, improving the power quality of the microgrid. The performance of the proposed control strategy is verified by using digital time- domain simulation studies in the PSCAD/EMTDC software environment.
Impacts of Energy Storage in Distributed[taliem.ir]

Impacts of Energy Storage in Distributed Power Generation: A Review

Distributed Generation (DG) in the form of Renewable Power Generation systems are currently preferred for clean power generation. However due to their intermittent and unpredictable nature, energy storage needs to be used to ensure that the load is met at all times. There are many possible options for energy storage and the most popular and technologically matured option, batteries, is the subject of this paper. This paper explores the importance and necessity of batteries within DG systems, especially with renewable power eneration systems. The paper looks at different varieties of batteries with a specifc emphasis on lead-acid atteries. To integrate batteries into renewable energy system models, the system and the energy storage, must be simulated to test the impact on as well as optimise the sizing of the system in terms of cost and efciency. As batteries are a fairly large capital investment in the system, it is crucial to ensure maximum life span. This is done by using a controller to control the charging and discharging cycles of the battery. There are currently many methods of modelling batteries as well as techniques for controlling the battery within the system. Some of these are discussed in this paper.
A Novel Hybrid Network Architecture to Increase[taliem.ir]

A Novel Hybrid Network Architecture to Increase DG Insertion in Electrical Distribution Systems

Distribution networks will experience a deep mutation concerning their planning and operation rules due to the expected increase of distributed generation (DG) interconnection to the grid. Indeed, the opening of the electricity market or the growing global concern for environmental issues will lead to a massive development of DGs. Yet, a too large amount of DGs could raise technical problems on distribution networks which have not been planned to operate with bi-directional power flow. The existing solutions to solve marginal DG connections could be no longer relevant. The distribution network definitely has to evolve towards a smarter and more flexible network. Two possible ways to reach this goal are through new architectures and developing intelligent systems. This paper focuses on new architectures and operating modes. The traditional radial distribution network could accept more DGs by introducing appropriately specific loops. A new hybrid structure enabling the coexistence of the radial and meshed operation is proposed. It is equipped with autonomous circuit-breakers and automated switches that improve its reliability. A heuristic algorithm is also proposed to build this new architecture while ensuring the equality of consumers with respect to the continuity of service and while minimizing the global cost.