Optimal Design of Conductive and Inductive Charging System for Bus

2020 IEEE PES/IAS PowerAfrica Optimal design of conductive and inductive charging system for bus rapid transit network Adedayo Asaolu Stuart Galloway Electronic and Electrical Engineering Electronic and Electrical Engineering University of Strathclyde University of Strathclyde Glasgow, United Kingdom Glasgow, United Kingdom [email protected] [email protected] Abstract— This paper proposes a multi-terminal allocation of B. Binary Variables charging infrastructure for the public bus transit network that ∝�, ∝�, ∝ℎ: Binary variable for low, medium and high priority charging integrates both inductive and conductive priority charging to � Binary variable for inductive charging ensure energy management without disrupting the operational bus schedule. The charging model is formulated as a C. Indices mathematical optimisation problem that allocates multi- �, �, � Indices for terminal, BEB and terminal position priority chargers for the transit network. The formulated in the transit networks optimisation problem is solved using a particle swarm �, � Indices for time steps optimisation (PSO) algorithm. The model is validated using �, � Indices for transit network battery electric buses (BEBs) Lagos BRT data. The results indicate that the integration of both inductive and multi-terminal conductive priority chargers in the transit system can serve as an energy I. INTRODUCTION management system and eliminate charging dwell time. Generally, developed countries are planning, and Keywords— Battery-electric bus (BEB), conductive charger implementing schemes for reducing greenhouse gas inductive charger, PSO, Transit network. emissions, and the critical focus is the electrification of the transport system (both public and private vehicles). NOTATION However, in the developing countries, the electrification of public transport and transit network is probable to evolve A. PARAMETERS ahead of individual owned vehicle because it can be �ℎ�� Charging priority selector controlled by government policy and deliberate investment �� Length of an inductive charger in public transport. Importantly, the power infrastructure for �� , �� Energy capacity of the BEB on arrival at the terminal/at public transport fleets is different from that for consumers the start of inductive charging �� as the charging infrastructures for the electric public �� BEB battery energy capacity �ℎ transport system are more of hub base [1] (i.e., terminals, �� Energy recharged via conductive charging deports and bus-stops) that can be power with renewable �� Energy gain from inductive charging energy mini-grids. Currently, in major European cities, 40- �� , �� Max, min Energy capacity of the BEB 60% of trips are achieved via sustainable means. In ��,�+� � Energy req. to travel from terminal i to i+n developing countries cities such as Lagos (Nigeria) that �� Energy received via inductive charging have a population of about 21millions people [2], this is �� Energy used to travel the inductive cable compounded. The characteristics of the transport system in �� ℎ Number of conductive chargers �� Lagos include the unavoidable daily experience of the worst ��ℎ Number of inductive chargers �� traffic situation due to road congestion and GHG emission ��ℎ Total number of chargers that are predominantly from automobiles [3]. Presently, �� , ��, �ℎ �ℎ �ℎ �ℎ Number of low, medium and high priority Lagos has a bus rapid transit (BRT) system that connects conductive chargers people from the suburbs to the central business district [4]. ��, �� Power of conductive and inductive chargers �ℎ �ℎ The greening of this public asset, in combination with �� Power used by inductive charger over time interval (t) (�) favourable GHG solutions, is an attractive option for �� , �� , �ℎ (�) (�) (�) Power used by low, medium and high priority conductive policymakers to eliminate ‘driveway’ congestion and charger over time interval (t) support the adoption of EV. �� , �� , �ℎ (��) (��) (��) Max. power capacity low, medium and high The development and adoption of Battery-Electric Buses priority conductive charger (BEBs) have been increasing rapidly within the last decade. � �� Power used by BEB per time step These vehicles offer zero-emission, quiet operation, high �� Power used by BEB when moving over inductive cable �� efficiency, reliability, and better acceleration compared to �(�) Power used by all the chargers in the transit with time �� traditional buses. In comparison to trolley bus technology, �� Arrival time of the BEB at the bus terminal �ℎ they eliminate the need for constant grid connection, and the �� BEB conductive charging duration � transit route can be modified without infrastructure change, �� The time the BEB is scheduled for the next trip i to i+n �� and the cost of ownership is lower than diesel buses [5]. �� Travelling time over induction cable �� In [6], the comparative on-road evaluation of diesel buses �� Waiting time of the BEBs at the terminals �,�+� with battery-electric buses BEBs is examined in a broad � Travel time from terminal i to i+n � range of circumstances. In this work, the BEBs cuts Petroleum Technology Development Fund, Abuja Nigeria, under grant number PTDF/ED/PHD/AAA/1085/17, sponsors the research work. 978-1-7281-6746-6/20/$31.00 ©2020 IEEE 2020 IEEE PES/IAS PowerAfrica petroleum use by 85–87% in comparison to a diesel bus and charging that occurs at the BEB terminals is assigned based attains a 32–46% decrease in the use of fossil fuel and 19– on the priority that depends on the state of charge of the 35% in CO2 emissions while evaluating from a life-cycle BEB battery on arrival at the terminal. perspective. The long routes (routes > 10km) within the transit Nonetheless, the charging systems that support long network are proposed to have inductive chargers; for driving distance are still in the early phases of development simplicity, they are located at the middle of the trip. This and very expensive. Moreover, the schedule for BEBs needs inductive charging stage occurs when the bus is either to consider a variety of parameters about the energy system moving slowly or is stopped for a few minutes to pick up [5],[7]. Mitigating these issues while observing the and drop off passengers. The BEB that can be charged operational bus schedules, the adequate provision for the inductively will contain additional equipment installed that trips demand energy needs to be considered. In the acts a 'pickup' device for collection of electrical energy from literature, different strategies have been proposed, and the the installed on-road power transmitters. This 'scavenged' common theme includes charging and battery swapping [8] charging will enable topping up of the BEBs batteries to [9] and repurposing infrastructure [11]. Under a battery extend their range and protect the BEBs batteries from over- swapping system, the BEB can replace its depleted battery drain. pack with a full one within a few minutes. Then the drain In this work, a similar modelling approach to that battery packs are recharged at the station and later swapped presented in [12] [13] has been adopted. While the focus in for other arriving BEBs [8][10]. However, the battery these leading research articles was to consider infrastructure swapping system requires a significant extra investment on requirements and grid effects respectively, here, a priority the batteries and its depot [11]. Hence, the majority of the charging scheme has been included, the option for ‘on-the- research work in BEBs have been concentrating on the fly’ inductive charging on longer routes made available and optimal sizing of battery and charging infrastructures to the context of the Lagos BRT accounted for. satisfy the BEBs transit operation plan [12]–[14]. The process flow diagram for the ‘modelled system’ As far as these authors are aware, previous research work shown in fig 4 is described as follows: has not considered: 1. Each BEB is operating on a fixed route within the BRT 1. The application of opportunity charging with the network; this fixed route has a terminal at both ends integration of renewable energy resources for a bus where the BEB can use conductive chargers. The routes transit system while taking note of the peculiarity of the that are longer than 10km have midway inductive cities in the developing countries such as the situation chargers. In addition, there are multiple bus stops to load in Lagos, Nigeria where the grid is weak, and traffic and unload passenger along each route. congestion is beyond problematic levels. 2. Each BEB is equipped with one battery unit denoted with �� 2. The use of both the conductive and inductive charging (�� ) in kWh, and all the BEB batteries are of the same system in a transit network to reduce the operational size. In this work, the BEBs batteries have a minimum �� downtime as a result of BEB charging duration. (�� ) and maximum (�� ) range of the total battery 3. The multi-terminal allocation of charging infrastructure energy capacity. for a bus transit system. �� 3. The arrival time (�� ), the battery energy capacity on 4. The priority charging method that ensures effective �� energy management at the conductive charging arrival (�� ) and the battery capacity (�� ) are terminals. logged on arrival at the BEB terminal. The duration In this work, the transit electrification system considered between the arrival and the next schedule is called stay is the multi-terminal allocation

Load more