In recent years, fully electric vehicles (EVs) have accounted for a higher proportion of urban buses. On account of their relatively short cruising range, many technologies were used to improve the driving range, such as improving energy management strategies and promoting the performance of the battery and engine. The purpose of this study was to develop an energy-efficient driving strategy to save energy. The strategy consists of two parts: determining a velocity interval for lower energy and establishing an energysaving acceleration mode. First, 30 velocity datasets were collected from an actual bus line. An electric bus model and energy consumption equation were established in the AVL CRUISE software to analyze the energy consumption. Next, the velocity interval was determined based on the actual data with the objective of maximizing engine efficiency and minimizing energy consumption. By considering uniform motion and traffic conditions, 30-40 km/h was determined as the velocity interval of lower energy for the electric bus mentioned in this paper. The acceleration characteristic parameter β represents the curve of velocity versus time in different acceleration processes, which was chosen to describe the acceleration mode; we found that when β is greater than 0.2, the lower the β value, the lower the energy consumption per kilometer was. Finally, the energy-saving driving strategy was verified by conducting a simulation. It was determined that the reduction in energy consumption per kilometer after implementing the energy-saving driving strategy was between 12.32% and 18.7% for short sections of acceleration and 2.47% for the entire bus trip.

Introduction

Electric vehicles have recently received a lot of attention because they are zero-emission vehicles and are more energyefficient than conventional vehicles. Electric buses have many advantages [1]–[۴], including being locally emissionfree, suffering no energy losses during idle operation, more energy-efficient than conventional buses, quiet, and able to recover braking energy. Due to the increasing oil crisis, an increasing number of electric buses have been put into operation in China. In Xi’an Shaanxi Province, the number of fully electric buses (often described as pure electric) has increased by more than 60% as of March 2019. Although electric buses have many advantages, the relatively short cruising range and long charging time are two major problems [5]. The fact that drivers worry about the range of the bus is a critical issue. According to a survey, when the battery state of charge (SOC) is about 40%, 80% of bus drivers will charge the vehicle instead of continuing to drive to prevent running out of battery power during the bus journey. In recent years, much research has focused on developing more energy-efficient vehicles [6], [7]. The energy efficiency of a vehicle depends on a number of factors; one factor is the hardware of the vehicle, such as the battery characteristics [8], electric motor characteristics [9], powertrain system [10], and charging device [11].