234 research outputs found
Energy management of community microgrids considering degradation cost of battery
No full textA storage system is a key component of a microgrid. Over the last few years, research has been undertaken to determine optimal management of microgrid resources. Battery storage has a significant impact on the total operational cost as the lifetime of the battery reduces during charging and discharging cycles. In this paper, we propose optimal energy management of a community microgrid in which the cost function includes the degradation cost of the battery and a dynamic penalty to reflect the true operational cost. Particle swarm optimisation (PSO) is used to determine the battery control actions for real-time energy management. Several case studies are presented to demonstrate the effectiveness of the proposed framework in which the new cost function reduces electricity cost by up to 44.50% compared to a baseline method and 37.16% compared to another existing approach
A coordinated voltage control approach for coordination of OLTC, voltage regulator, and DG to regulate voltage in a distribution feeder
No full textIntegration of small-scale electricity generators, known as distributed generation (DG), into the distribution networks has become increasingly popular at the present. This tendency together with the falling price of the synchronous-type generator has potential to give DG a better chance at participating in the voltage regulation process together with other devices already available in the system. The voltage control issue turns out to be a very challenging problem for the distribution engineers since existing control coordination schemes would need to be reconsidered to take into account the DG operation. In this paper, we propose a control coordination technique, which is able to utilize the ability of DG as a voltage regulator and, at the same time, minimize interaction with other active devices, such as an on-load tap changing transformer and a voltage regulator. The technique has been developed based on the concept of control zone, line drop compensation, dead band, as well as the choice of controllers' parameters. Simulations carried out on an Australian system show that the technique is suitable and flexible for any system with multiple regulating devices including DG
A novel tuning method for advanced line drop compensator and its application to response coordination of distributed generation with voltage regulating devices
No full textNowadays, integration of small-scale electricity generators, known as Distributed Generation (DG), into distribution networks has become increasingly popular. This tendency together with the falling price of DG units has a great potential in giving the DG a better chance to participate in voltage regulation process, in parallel with other regulating devices already available in the distribution systems. The voltage control issue turns out to be a very challenging problem for distribution engineers, since existing control coordination schemes need to be reconsidered to take into account the DG operation. In this paper, a control coordination approach is proposed, which is able to utilize the ability of the DG as a voltage regulator, and at the same time minimize the interaction of DG with another DG or other active devices, such as On-load Tap Changing Transformer (OLTC). The proposed technique has been developed based on the concepts of protection principles (magnitude grading and time grading) for response coordination of DG and other regulating devices and uses Advanced Line Drop Compensators (ALDCs) for implementation. A distribution feeder with tap changing transformer and DG units has been extracted from a practical system to test the proposed control technique. The results show that the proposed method provides an effective solution for coordination of DG with another DG or voltage regulating devices and the integration of protection principles has considerably reduced the control interaction to achieve the desired voltage correction
Enhanced frequency response strategy for PMSG based wind energy conversion system using ultracapacitor in remote area power supply systems
No full textMultilevel energy storage based frequency regulation in remote area power supply systems
No full textEffects of PEV Penetration on Voltage Unbalance
No full textBalancing loads in low voltage networks is a challenging task due to a continuous fluctuation in the power demand. Voltage unbalance is a condition in which the voltage phasors differ in amplitude and/or do not have its normal 120° phase relationship. This has a potential to introduce technical issues that lead to a costly phenomenon for power distribution system due to the high penetration of Plug-in Electric Vehicles (PEVs). Voltage unbalance study is essential as the propagation of zero sequence component in the distribution system is limited by transformer winding connections and network grounding. Indeed, single phase loads are not affected by unbalance unless the unbalance causes over or under voltages which exceed the acceptable limits. However, the large numbers of PEVs charging from single phase residential feeders of distribution networks may exceed the statutory limits. This chapter presents theoretical discussion with analytical framework for modeling the effects of voltage unbalances due to PEV penetration. A PEV charging profile of a conventional PEV battery has been employed with the daily load demand to synthesize the dynamic effect of PEV penetration. A distribution network topology has been used with unbalanced allocation of single-phase loads and PEVs connected in four-wire, three phase network to investigate the effects of PEV charging on the feeders subject to voltage unbalance. Furthermore, the chapter explores the application of PEV load balancing strategy in the context of smart grid to mitigate the effects of unbalanced allocation of PEVs
Behavioral characterization of electric vehicle charging loads in a distribution power grid through modeling of battery chargers
No full textPlug-in Electric Vehicle (PEV) is a new atypical
load in power systems. In future, PEV load will play a significant role in the distribution grids. This integrated load into the power grid may overload the system components, increase power losses and may violate system constraints. Currently, the most common method of Electric Vehicle (EV) modeling is to consider the EV
loads as constant power elements without considering the voltage dependency of EV charging system during state of charges (SOC). EV load demand cannot be considered as a constant power, as modeling as a constant power load will not provide accurate information about the behavior of charging system during charging process. As several research projects on smart grids are now looking into realistic models representing the realistic behavior of an EV loads, this paper proposes a methodology for modeling of EV charger integrated to an electricity grid in order to understand the impacts of EV charging load. A charging system was designed to capture the EV load behavior and extract the coefficients of the EV ZIP load
model. A comparative study was carried out with different types of load models. The results indicate that the assumptions of load demand as a constant power to analysis the effect of PEVs on power grid would not be effective in real time application of PEVs
Behavioral characterization of electric vehicle charging loads in a distribution power grid through modeling of battery chargers
No full textThe plug-in electric vehicle (PEV) is a new atypical load in power systems. In future, PEV load will play a significant role in the distribution grids. This integrated load into the power grid may overload the system components, increase power losses, and affect the voltage profile in the distribution systems. Currently, the constant power load model is most commonly used for the modeling of the electric vehicle (EV) load that considers the EV loads as constant power elements without considering the voltage dependence of the EV charging system. EV load demand cannot be considered as a constant power due to the fact that modeling as a constant power load will not provide accurate information about the behavior of the charging system during the charging process. In this paper, an accurate model representing the realistic behavior of EV load is developed which is based on the ZIP load model with the ZIP parameters established through the realistic EV load data. The proposed model can be used to analyze the true behavior of the EV charger integrated to an electricity grid and determine the impacts of EV charging load on the grid. A realistic charging system was used to test and capture the EV load behavior and extract the coefficients of the EV ZIP load model, which have been verified using computer simulations and laboratory experiments. Additionally, a comparative study between the proposed ZIP load model and the constant power load model was carried out, and the results were verified with the practical EV load data. The results confirm that EV represented using constant power load will not provide the true reflection of the EV load behavior and the EV impacts on the power grid
A decentralized model predictive control for multiple distributed generators in the islanded mode of operation
No full textEvaluating the effectiveness of a machine learning approach based on response time and reliability for islanding detection of distributed generation
No full textConventional relays, such as vector surge relay, frequency relay and rate-of-change-of-frequency relay, are usually employed for islanding detection; however, these conventional relays fail to detect islanding incidents in the presence of small power imbalance inside the islanded system. This study presents an islanding detection approach for synchronous type distributed generation using multiple features extracted from network variables and a support vector machine (SVM) classifier. Features are extracted from a sliding temporal window, whose width is selected so as to achieve the highest detection rate at a fixed false alarm rate. The SVM classifier is trained with linear, polynomial and Gaussian radial basis function kernels, and the parameters of the kernels are tuned to improve the classification performance. The application of the proposed method is illustrated for islanding cases associated with different power imbalance conditions, including small power imbalance conditions associated with the non-detection zone of conventional relays. Furthermore, variation of detection time as a function of power imbalance scenarios, which involve all probable combinations of deficit of active/reactive and excess of active/reactive power imbalance, is assessed in the testing phase. The performance of the proposed approach is evaluated and compared with those of conventional relays in terms of reliability and response time of islanding detection
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