Joy Chandra Mukherjee

A Review of Charge Scheduling of Electric Vehicles in Smart Grid

Electric vehicles (EVs) are being introduced by different manufacturers as an environment-friendly alternative to vehicles with internal combustion engines, with several benefits. The number of EVs is expected to grow rapidly in the coming years. However, uncoordinated charging of these vehicles can put a severe stress on the power grid. The problem of charge scheduling of EVs is an important and challenging problem and has seen significant research activity in the last few years. This review covers the recent works done in the area of scheduling algorithms for charging EVs in smart grid. The works are first classified into two broad classes of unidirectional versus bidirectional charging, and then, each class is further classified based on whether the scheduling is centralized or distributed and whether any mobility aspects are considered or not. It then reviews the key results in this field following the classification proposed. Some interesting research challenges that can be addressed are also identified.

Distributed Charge Scheduling of Plug-In Electric Vehicles Using Inter-Aggregator Collaboration

Plug-in electric vehicles (PEVs) are emerging as an eco-friendly and cost-effective alternative to conventional vehicles driven by internal combustion engines. However, uncoordinated charging of a large number of PEVs may cause grid failure. Therefore, charge scheduling of PEVs is an important problem. However, the charge scheduling by a single aggregator does not scale well as the PEV population grows. We propose a distributed framework for efficient PEV charging with multiple aggregators in a city where a PEV raises its charging request to a specific aggregator, and each aggregator has partial information about others. The aggregators collaborate among themselves for scheduling PEVs for charging in different charging stations owned by it or others. In this paper, we formulate a bi-objective charge scheduling optimization problem that attempts to maximize the total profit of the aggregators while maximizing the total number of PEVs charged. We first prove that the problem is NP-complete. We then propose distributed offline and online algorithms to solve the problem, and present simulation results for some realistic traffic scenarios.

Event Notification in VANET With Capacitated Roadside Units

Many future vehicular ad hoc network (VANET) applications will be event driven and will require events of different types to be delivered to moving vehicles within some specified time. In this paper, we propose a publish-subscribe based event notification framework that uses roadside units (RSUs) to deliver events to vehicles that subscribe to them within the validity periods of both the subscriptions and the events. Each RSU can disseminate only a finite number of events at a time and has a cost associated with it. Two scheduling problems to schedule the dissemination of events from RSUs are formulated. The first problem aims to maximize only the number of subscriptions that are matched to some events. The second problem, in addition to maximizing the number of subscriptions matched, also aims to minimize the total cost of disseminating the events. We have designed offline and online algorithms for the problems that a service provider can execute to schedule event disseminations from the RSUs. Detailed simulation results are presented to show that the algorithms are able to match a high percentage of subscriptions with low average event dissemination cost for some realistic city traffic scenarios.

Distributed event notification in VANET with multiple service providers

Many future applications in vehicular networks will be event-driven and will require events generated at different parts of a city to be delivered to moving vehicles in time. We propose a distributed framework for efficient event dissemination with multiple service providers (SPs) in a city where each SP uses a publish-subscribe communication framework using roadside units (RSUs). SPs know only about their own subscriptions and events, but have no knowledge about the subscriptions and events of other SPs. In this paper, we propose a problem called the Bounded Minimum Cost Event Placement Problem where SPs collaboratively schedule the dissemination of the events through RSUs so that maximum number of subscriptions are satisfied while incurring minimum cost to the SPs. We propose a distributed algorithm to solve the problem and present initial simulation results for some realistic traffic scenarios.

A mobility aware scheduler for low cost charging of electric vehicles in smart grid

Electric vehicles (EVs) can charge their battery from smart grid (G2V) through charging stations located at different parts of the city. However, charging of EVs in a large scale without coordination to the grid may cause grid failure. Therefore, coordinated charging of EVs is an important problem. In this paper, we formulate a bi-objective charge scheduling optimization problem that attempts to minimize the average charging cost while maximizing the number of EVs charged. We refer to this problem as the Minimum Cost Maximum EV Charging Problem where mobile EVs communicate their charging preferences apriori to the aggregator and the aggregator schedules EVs to different charging stations in their route so that the objective is met, and the grid remains safe. We first prove that the problem is NP-complete in the strong sense. An upper bound is proved for the number of EVs charged. Two greedy heuristics are then proposed to solve the problem. Detailed simulation results for different city traffic scenarios show that the number of EVs charged as achieved by the heuristics proposed is close to the upper bound proved with reasonably low cost.

A publish-subscribe based framework for event notification in vehicular environments

In this work, we consider a vehicular environment in which vehicles moving along roads in a city are interested in different types of information or events generated at different parts of the city. We investigate the use of the publish-subscribe framework for such environments in which vehicles subscribe to a service provider for specific types of events through roadside units; the events are also reported to the service provider. The service provider delivers the events to the subscribed vehicles within the validity periods of both the subscriptions and the events through roadside units placed along the trajectory of a vehicle. We propose a problem called the Minimum Cost Event Placement Problem which addresses the issue of delivering all the events to all the subscribed vehicles within the validity periods while incurring minimum cost of utilization of the roadside units. We first prove that the problem is NP-complete. We then propose three heuristic algorithms to solve the problem. A lower bound on the cost of utilization of the roadside units for a given set of subscriptions and events is presented next. Detailed simulation results in different city traffic scenarios are presented to show that the costs achieved by two of the heuristics proposed are close to the lower bound proved.

Mobility Aware Event Dissemination in VANET

Many future VANET applications will be event-driven and will require events of different kinds to be delivered to vehicles en route in time. In this work, we propose a publish-subscribe based communication framework for a service provider (SP) that utilizes its roadside units (RSUs) to deliver relevant events to moving vehicles. Vehicles subscribe to a SP for specific types of events; the events are also reported to the SP. The SP delivers the events to the subscribed vehicles within the validity periods of both the subscriptions and the events through RSUs placed along the route of the vehicles. The problem is referred as the Minimum Cost Event Placement Problem [10] that schedules the placement of events in RSUs for different time intervals so that the events are delivered to the subscribed vehicles while incurring minimum cost of utilization of the RSUs. In this paper, we give a ln n approximation algorithm for the problem, where n is the number of subscriptions. We then propose a centralized online algorithm to solve the problem. A lower bound on the cost of utilization of the RSUs for a given set of subscriptions and events is presented next. Detailed simulation results in realistic city traffic scenarios are presented to show the performance of the algorithms.

Mobility Aware Charge Scheduling of Electric Vehicles for Imbalance Reduction in Smart Grid

Electric vehicles EVs are being introduced by different manufacturers as an environment-friendly alternative to vehicles with internal combustion engines. The number of EVs is expected to grow rapidly in the coming years which will act as distributed loads in the demand side of the smart grid. On the supply side, an aggregator has to predict a load schedule 12-36 hours in advance to charge the EVs and purchase energy accordingly from the day-ahead market. The goal of the aggregator is to schedule the charging of EVs at different charging stations so that the load prediction made by the aggregator are met and the energy imbalance between the energy purchased and the energy consumed by the EVs is minimized. In this work, we refer to this problem as the Maximum Energy Usage EV Charging Problem where mobile EVs communicate their charging preferences apriori to the aggregator and the aggregator schedules EVs to different charging stations in their route so that it incurs maximum energy usage and therefore, minimum energy imbalance. We first prove that the problem is NP-complete. A pseudo-polynomial algorithm is proposed for a restricted version of the problem that can act as an upper bound for the solution of the general problem. A greedy heuristic is then proposed to solve the problem. Detailed simulation results in different city traffic scenarios show that the usage of energy achieved by the heuristic proposed is close to the upper bound proved.