**1. Introduction**

Today, about 20% of the global primary energy usage and about 25% of energy-related emissions of CO2, are due to the contribution of the transportation field [1]. Moreover, half of the emissions for transportation originate from passenger vehicles, mostly based on the internal combustion engine (ICE) propulsion [1]. One of the most promising technologies to solving the above issues is represented by electric vehicles (EVs), including hybrid EVs (HEVs), thanks to the cut of oil usage and of CO2 emissions, on a per-km basis [2].

EVs will play a major role in meetings Europe's need for clean and efficiency mobility. The objectives set in the European Green Vehicles Initiative (EGVI) report [3] are quite ambitious; an overall efficiency improvement of the transport system by 50% in 20 years (i.e., in 2030 compared to 2010). The major EV car manufacturers have started the production and sale of EVs, with projections estimating one million EVs circulating in Europe by 2020, anticipating a significant expansion by 2030 and beyond. More than that, the sales of new electric vehicles worldwide exceeded one million cars in 2017 [4]. This market volume represents a huge growth in the sales of new electric cars, by 54% compared with 2016 [5]. In some countries, the market of electric cars is no more a niche market; for example, in Norway, the market share of electric cars, in terms of new car sales, was 39% in 2017 [6]. More than half of the global sales were in China, more than double the amount delivered in the United States [7,8]. The global stock of electric vehicles is growing rapidly and was already beyond the threshold of three million vehicles in 2017.

To reduce the emission of pollutions (e.g., CO2 and NOx), the main trend in new vehicle design is electrifying the propulsion [9–19]. The evolution towards electric/hybrid mobility has been accelerated by the so-called "diesel gate" in Europe and the United States [20,21], as well as by the high economic cost for cars equipped with conventional ICE, to face restrictive regulations regarding greenhouse gases. Beside low-volume premium car brands, like Tesla, several large-volume car makers announced a cut in all petrol/diesel vehicles (e.g., by 2019, all new car models from Volvo and those produced in Europe by Toyota will be fully electric and/or hybrid). By 2030, a ban of diesel car sales has been announced by several countries.

Together with the increased connectivity of the car with the smart grid, thanks to V2SG/V2I (vehicle to smart-grid/infrastructure) wireless technology, the cars of the future will be electrified, connected, shared, and autonomous. The major impacts of the current R&D activities in academia and industry will be as follows:


Unfortunately, full EVs are expensive, mainly because of the cost of the battery-based energy storage. Moreover, the autonomy of full EVs is still not comparable to ICE-based ones. A full EV needs also a rethinking of the drivetrain architecture, which now should involve high voltage power buses (up to 300 V or 400 V), with extra shock protection and insulating costs, power electronic converters, battery energy storage with battery management systems, new electric machines, and new transmission schemes. Indeed, as an alternative to the classic solution of a single-engine plus a complex transmission sub-system, constructions with a dedicated motor per driving wheel (two or four) are proposed. Electrical machines on-board electrical vehicles should have power levels ranging from tens of kWs, in cases of light vehicles or in cases of one motor for each driving wheel, to hundreds of kWs. Because of large time and development costs, the widespread diffusion of electric vehicles on the market is still to come.

Hence, the hybridization of the propulsion is the most viable solution to ensure, in the short term, a smooth transition from classic petrol/diesel cars to fully electric ones. Hybrid vehicles still need the evolution of current power electronic/electric parts of ICE cars; classic alternators should evolve towards an integrated starter-generator, capable of providing torque assistance to the ICE at low rpm conditions (motor mode), or to generate electric energy when the vehicle is braking or the ICE is working at a high rpm (generator mode). The classic 12 V power bus should evolve to a 48 V bus, in order to increase the power delivered with the same current levels. Several Original Equipment Manufacturers (OEMs) already succeeded in launching/going onto the mass market with 48 V topologies, with an acceptable cost level reaching the CO2 emission targets and solving the technical challenges in areas such as battery technology, power electronics, EMC, and the electrification of further features.

The development of new tools, functionalities, and methods integrated with the controlled development of a vehicle-centralized controller will also be part of the future solutions for the next generation of EVs. For improving on the safety analysis and reduction costs, the solutions will be based on flexible user-friendly interfaces and specialized software tools, as well as on Ethernet, according to the existing ISO/IEC standards. The current trends is integrating Ethernet with other communication domains using already established technologies in the automotive industry, such as Controller Area Network (CAN), Local Interconnect Network (LIN) protocol, and Flex-Ray. These new technologies, based on digitalization and connectivity, will enable new ways to structure and design electric and

electronic (E/E) architectures, such as seamless hierarchical architectures, for the next generation of cars.

As a matter of fact, digital technologies are already used in energy end-use sectors, and new technologies with the potential for widespread deployment are appearing, such as autonomous driving, intelligent domotic systems and machine learning. These platforms offer a high performance and fulfil the highest security and safety requirements [4,22].

The implementation and validation of tools under real-driving conditions based on the Internet of Things (IoT) paradigm for the over-the-air (OTA) diagnostic and flashing, and for V2SG issues, will also be part of future solutions. OTA will cut the time and cost for electronic control unit (ECU) diagnostic and reprogramming by at least 50% in case of software (SW) bugs.

To address the above issues, this paper reviews recent trends in green vehicle electrification. Particularly, Section 2 refers to the energy demand and emissions of EVs, and reviews the battery technology trends, including recharging issues and solutions, to integrate the EV electricity demand in power grids. Sections 3 and 4 deal with the integrated electric/electronic architectures and control systems of new generations of hybrid and full electric vehicles. The increased digitalization and connectivity of cars is posing cyber-security issues, which are discussed in Section 5. Conclusions are drawn in Section 6.
