Meeting the Design Challenges of Electric Vehicle Charging Systems

Electric Vehicles Charging requires more than just an outlet in the driveway of a charging station. The increase in the number of electric vehicles has increased the demand for electricity, and it will also require improvements in grid management systems, more efficient chargers, and integrated home energy management.

There is a huge demand for smart charging and faster charging at home and in the office, which requires a shift from AC chargers to DC chargers. In addition, there are safety issues to consider, including certification of electric vehicle batteries. Users also want to be able to charge anywhere, pay securely anytime, anywhere, and link charging to a single central account and bill.

Safety is the core

Charging solutions must use secure elements to meet industry standards such as ISO 15118 or relevant calibration regulations (such as Germany's Eichrecht). For example, NXP's latest EdgeLock® SE05x family of embedded security solutions helps ensure that the entire value chain is safe from cyberattacks while ensuring security and ease of use at the connection point.

To avoid unauthorized access, EV charging stations can be unlocked with credentials such as physical smart cards or smartphones using a security protocol based on industry-standard NFC. These features also support other smart city applications such as parking and public transportation. NXP’s smart card solutions are able to leverage its large MIFARE® contactless ecosystem established in more than 750 smart cities around the world.

Get more information. Learn more about electric vehicle charging stations now.

power ups

Many charging stations use AC power. Usually single-phase, but three-phase is increasingly being used. There are a small but growing number of HVDC charging stations. Compared to AC stations, HVDC stations offer higher power and faster charging times. Therefore, most EV OEM suppliers want to co-develop both charging methods. This means they can benefit from NXP’s technology components to simplify development and increase reuse.

Electric Vehicle Charging Solutions

Charging stations, or Electric Vehicle Power Equipment (EVSE), in addition to interacting with users, also need to communicate with the grid to implement functions such as load balancing, vehicle-to-grid (V2G) (compliant with ISO 15118 standard), smart charging, open charge point protocol (OCPP) and charging.

ISM and mobile networks can be added to the communications technologies using NXP’s IW620 dual-band solution (combining Wi-Fi® and Bluetooth), or using the OL2385 RF transceiver for sub-GHz protocols. These technologies can be used in conjunction with devices such as the LPC55S69 , which is ideal for NBIoT implementations, as well as wired communications devices such as PLCs .

Closely related is the SE05x-based security function block, which provides authentication using end-to-end encryption to enable the exchange of sensitive information such as billing data. It also manages the data exchange between the on-board charger (OBC) and the backend server.

This controller board will manage the main functions and services, such as high-level communications, through the safety and external communication modules, and run the protocol stacks used in EVSE applications. These include the ISO 15118 standard defined for V2G communications and possibly OCPP. NXP processors are available in a wide performance range, from the MIMX8xx MPU application processors to the MIMXRT11xx family based on the Arm® Cortex®-M7 real-time MCU core, to the latest LPC55x family of Cortex-M33 based MCUs.

EVSE system view

Smart Charging

Smart wall boxes and charging stations are typically cloud-connected. Connectivity between the consumer, charging station, and cloud is typically handled via Ethernet or Wi-Fi 6, Zigbee®, or other wireless technologies. Smart charging stations are often combined with smart metering solutions, increasing the amount and complexity of data processing.

Charging station cloud connection (cloud registration) requires a simple provisioning and authentication process to maintain high security. NXP supports the zero-touch registration process of major cloud partners through its SE05x and EdgeLock 2GO service, which also authenticates sensitive user data such as consumption records and payment data.

In addition, serving autonomous vehicles also places new demands on charging stations. Autonomous vehicles need to accurately navigate to charging stations to charge, without the need for humans or (expensive) robotic assistants to provide the last centimeter of connection. This can be achieved by relying on high-precision positioning wireless technologies such as ultra-wideband (UWB), allowing autonomous vehicles to accurately guide themselves to the right location.

Cloud Connectivity Reference Design

Our cloud-connected electric vehicle charging station reference design, EasyEVSE, integrates multiple NXP products to help customers accelerate innovation and simplify the design process. Customers can quickly load Azure RTOS-based application software on NXP's i.MX RT1064 crossover MCU and securely connect the simulated electric vehicle charging station to Microsoft Azure IoT Central. The reference design uses NXP's Kinetis® metering MCU, which includes its own reference design, schematics and metering software. Because secure communication is required between the car, EV station and the cloud, this reference design shows how to use NXP's EdgeLock secure element to meet ISO 15118 information security and functional safety requirements. Customers can use this platform as the basis for a complete and differentiated EVSE system.

Local storage for electric vehicle charging

As charging stations move from AC to DC, the grid must meet peak demand for high power (350 kW or more) output, with battery voltages up to 1000 V. Local storage can solve this problem using batteries and NXP's battery management system (BMS). When the local battery is fully charged, it can deliver power to the electric vehicle first, and then draw more power from the grid.

When there are no electric vehicles charging, local batteries can be charged from the grid or even on-site solar arrays to relieve peak demand on the grid and ensure power supply during power outages. Achieving local power balancing requires a battery management unit (BMU), which includes NXP's FS32K series, power management ICs that support functional safety, BMS gateways that support software-free battery packs, and high-precision analog front ends that provide battery status values.

Conclusion

As electric vehicles become more and more popular, a large number of safe and reliable charging stations need to be developed.

NXP has extensive experience in power conversion as well as secure data transactions and device authentication. In EV charging, these two areas come together in a new way.

With a growing number of evaluation kits and reference designs covering most needs for AC and DC charging stations, NXP is ready to support the rapid growth of the electric vehicle industry by offering advice to manufacturers and service providers.

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author:

Mark Swinburn

Head of EMEA Electric Vehicle Charging Equipment and Smart Home Appliances at NXP Semiconductors

Mark has over 30 years of experience in electronic design and has been responsible for MCU, Connectivity and Security at NXP for the past decade.