Two-Area Control of Emergency Frequency Regulation Through Aggregation of Electric Vehicles

Frequency control has become more of a concern for the reliable operation of interconnected power systems. Due to the integration of low inertia renewable energy sources into the grid and their volatility, there is a need for emergency frequency regulation and nonlinear control of the power system in case of large disturbances incorporating quick response loads such as Electric Vehicles (EV)s. Some published literature has studied the profits that EV owners can gain by participating in frequency regulation and focused more on the contract design among different entities. Some studies have addressed how much power the EVs can provide for the grid in case of the need for frequency stabilization. However, the contribution of EVs to emergency frequency regulation in a wider area network has not been studied yet, which is the main focus of this research. In this work, the control methods are primarily based on the aggregation of EVs injecting power into grid, and the frequency control system design is such that the grid-connected EVs aim at maximizing the reduction rate of the total kinetic energy of the system based on Lyapunov energy function. The performance of the control law was evaluated in a two-area network and with different locations of aggregated charging stations in the corners or in the middle of the interconnected network. At this stage, a big virtual EV is connected to each connected area and the control inputs are formulated with no constraint on the connected EVs. However, there is always a constraint on the maximum allowed penetration of EVs to the grid without any voltage violations on any nodes of the distribution network. In chapter 4, a model is proposed for aggregation of EVs in each area at distribution network level, in which the contribution of EVs for frequency regulation is proportional to the frequency deviation and EVs’ available energy. Then, the aggregate model is developed based on the probability distribution of number of EVs and their initial State of Charge (SOC) and energy. The simulation is initially done for two cases: 1- number of EVs to be fixed and their available energy to be random with a uniform distribution, 2- EVs’ energy to be fixed and random number of EVs with a binomial distribution. In the same chapter, the impact of aggregate model on distribution network is studied to find the safe penetration rate of EVs under the worst case scenario where all the points in a charging stations are connected to an EV. An EV-MPM algorithm is proposed to find the safe penetration rate of connected charging stations in a distribution network based on load-flow analysis and the voltage of any of the nodes not exceeding the maximum limit of 10% violation. The algorithm is tested on an IEEE 31 node 23 kV distribution system with five charging stations connected to the nodes. Given the day-ahead load profile, the daily safe penetration rate of EVs is estimated for a typical day. The derived penetration rate is then used in the aggregate model of virtual EV, and simulated in a two-are network to represent the emergency frequency control of connected EVs when contingency occurs in the system. The main contribution of this study is proposing a holistic layered structure to estimate the contribution of EVs from the distribution network level to a wider-connected areas, which hasn’t been addressed in the literature

Investigation of GIC effects on core losses in single phase power transformers

This paper presents a method for estimation of core losses in banks of single phase power transformers that are subjected to an injected DC current such as geomagnetically induced currents (GIC). The main procedure of the core loss calculation is to obtain a magnetic flux density waveform in both time and location by using a novel algorithm based on 3D FEM inside the core and then to calculate the loss distribution based on loss separation theory. Also, a simple and effective method is proposed for estimation of losses of asymmetric minor loops by using combination of symmetric loops. The effect of DC biasing on core losses in single phase power transformers is investigated and the sensitivity of core type and material is evaluated. the results shows that DC current biasing could increase core losses up to 40 percent or even more

Prévention de la transmission mère-enfant de l’hépatite B

La transmission mère-enfant du virus de l'hépatite B est la principale cause de portage chronique de l'AgHBs. La prévention de cette transmission repose principalement sur la sérovaccination du nouveau-né. En France, le dépistage prénatal de l'AgHBs est obligatoire au sixième mois de la grossesse chez toutes les femmes enceintes. Lorsque la recherche de l'AgHBs est positive chez la mère, le nouveau-né doit recevoir dès sa naissance, par voie intramusculaire et dans deux sites différents, une première injection de vaccin et une injection d'immunoglobulines anti-HBs. La vaccination est ensuite poursuivie selon le protocole recommandé. L'efficacité de la sérovaccination est supérieure à 90%, elle doit être contrôlée chez tous les enfants par un examen sérologique (AgHBs et anticorps anti-HBs) effectué à distance de la dernière injection vaccinale entre 9 et 12 mois après la naissance. Les échecs de la sérovaccination s'observent chez des femmes ayant une charge virale élevées (HBV-DNA >200 000 UI/ml). Chez ces femmes, un traitement antiviral en fin de grossesse et durant le premier mois du postpartum par un analogue nucléosidique ou nucléotidique (lamivudine, telbivudine, ou ténofovir) permet de réduire la fréquence des échecs de la sérovaccination. L'objectif était d' étudier l'efficacité du traitement antiviral associé à la sérovaccination pour la prévention de la transmission mère-enfant du virus de l'hépatite B.Patients et méthodes: il s'agit d'une étude rétrospective incluant toutes les femmes enceintes AgHBS positif suivis en consultation dans le service d'hépato-gastroentérologie de l'Hôpital Tenon de Paris pendant une période allant de 2000 à 2013. Nous avons au cours de la période d'étude trouvé 23 femmes AgHBs positif mères de 37 enfants ont été suivies. Soixante-treize pour cent des femmes incluses étaient d'origine asiatique avec un âge moyen de 27 ans (extrêmes: 19-37 ans). Dans 81% des grossesses les femmes ont été traitées par un analogue nucléo(ti)que (lamivudine ou ténofovir). Parmi elles 68% avaient une charge virale supérieure à 5 logs au début du traitement. Quatre-vingt-dix-sept pour cent des enfants ont reçu une sérovaccination à la naissance mais seulement 86% d'entre eux avaient un schéma vaccinal complet. Soixante-treize pour cent des enfants ont eu à l'âge de 7 à 12 mois une sérologie de contrôle de la transmission (AgHBs) et de l'efficacité vaccinale (AC anti-HBs). Dans 96% l'immunité obtenue était satisfaisante avec un taux protecteur d'AC anti-HBs. le traitement par la lamivudine ou le ténofovir des femmes porteuses d'une hépatite B chronique avec une charge virale B élevée au 3ème trimestre associé à la sérovaccination du nouveau-né dès la naissance permet une prévention efficace de la transmission verticale du VHB

Aggregation of electric vehicles for emergency frequency control of two-area interconnected grid

Frequency control has become more of a concern for the reliable operation of interconnected power systems due to the integration of low inertia renewable to the grid. Electric Vehicle (EV)s have the potential to cooperate in emergency frequency control by a nonlinear control of the power system in case of large disturbances. An aggregate model is necessary for a quick response to prevent from much frequency deviation and the occurrence of any blackout. In this work, an aggregate of EVs is modeled as a virtual battery, considering the stochastic number of connected EVs and their initial State of Charge (SOC). A control strategy is applied to the aggregate model, using Lyapunov energy function, to maximize the rate of reduction of total kinetic energy in a two-area network after a fault event. The simulation results revealed that EVs can help the generator lose its kinetic energy in a short time after a contingency.</p

Frequency control impact of electric vehicles on grid-connected areas

This paper presents an emergency frequency control potential of Electric Vehicles (EV)s in a wide area network. Lyapunov energy function is used to maximize the rate of reduction of total kinetic energy in a two-area grid after a contingency event. The effectiveness of the proposed control strategy on damping the oscillations is studied, exploring the locations aspect of the model with the charging stations either in the center of grid-connected areas or in the corners.</p

Core loss behavior in high frequency high power transformers—II: Arbitrary excitation

High frequency high power transformers used in power electronic converters are frequently subjected to non-sinusoidal excitations. The main purpose of this paper is to study the effects of some general arbitrary waveforms on magnetic core loss in these transformers. First, using well-known empirical equations, general expressions were derived based on the parameters of the waveforms. Second, the impacts of different orders of voltage harmonics were investigated. Finally, capabilities of nanocrystalline and amorphous magnetic materials were compared. It is shown that the loss inside the core is highly sensitive to the rise time and duty cycle of trapezoidal and rectangular waveforms, respectively. Furthermore, although amorphous materials have higher saturation flux density, the total core loss inside the transformer designed using nanocrystalline material is considerably lower than the similar transformer with amorphous materials

On the Optimum Design of Air-Cored Tesla Transformers

In this paper, the effect of mutual inductance (M) and its optimization on the output pulse rise time in Tesla coils is investigated. A numerical method is proposed to calculate the mutual inductance in a Tesla coil. The method is verified by performing some experiments. Eventually, the conditions for maximum voltage gain for ordinary Tesla coil and autotransformer connected one are surveyed