cRIO platform helps develop electric vehicle charging system

Abstract: NI CompactRIO and rapid software development based on the NI LabVIEW software platform provide powerful tools for various rapid prototyping and hardware-in-the-loop simulations. The development of electric vehicles is changing with each passing day, and the development of charging systems urgently needs this fast and efficient development mode - rapid prototyping and hardware-in-the-loop.

NI CompactRIO is an ideal platform for rapid prototyping. It is a compact and rugged industrial control and acquisition system that uses reconfigurable I/O (RIO) and FPGA technology to achieve ultra-high performance and customizable functions. NI CompactRIO includes a real-time controller and a programmable FPGA chip, which is particularly suitable for independent embedded or distributed applications with strict reliability requirements; it also includes hot-swappable industrial-grade I/O modules, which have built-in signal conditioning and can be directly connected to sensors/brakes. Because CompactRIO has a low-cost open architecture, users can easily access the underlying hardware devices. In addition, CompactRIO embedded systems can be quickly developed using efficient LabVIEW graphical programming tools.

According to the definition of "General Requirements for Electric Vehicle Charging Stations", a charging station is composed of three or more off-board chargers and (or) AC charging piles for electric vehicles (at least one off-board charger), which can charge electric vehicles and monitor the status of chargers and power batteries during the charging process. Its system includes: power supply system, charging system, monitoring system (including: power supply monitoring system, charging monitoring system and safety monitoring system), as shown in Figure 1. The research and development of charging equipment is mainly divided into two parts: charging system and monitoring system.

Hardware in the Loop

Hardware-in-the-loop (HIL), also known as semi-physical simulation, refers to the use of hardware I/O to simulate the behavior of real controlled devices to verify the performance of the controller. As the central nervous system of the charging station, the monitoring system must have real-time, reliable, stable and safe characteristics. Before applying the controller to the actual system, it is best to conduct hardware-in-the-loop simulation experiments. The introduction of this link can ensure that the embedded software is tested early in the development cycle, so as to find problems early and reduce the cost of solving problems.

The monitoring system monitors, protects, controls, manages, and processes the operation of the charger and the charging process of the power battery, handles emergencies in the event of an accident, and stores, displays, and collects statistics.

The core of the charging station is the charger, the monitoring system is the network hub, and the battery system of the electric vehicle is the service object. Applying rapid prototyping and hardware-in-the-loop technology to the R&D system of charging equipment will greatly improve R&D efficiency and reduce R&D costs. Juxing Instruments uses LabVIEW as the software platform and NI's reconfigurable I/O as the hardware platform to build a charging equipment R&D architecture as shown in Figure 3.

The functions of each part in Figure 3 are as follows:

(1) Monitoring master station and power supply monitoring system

The functions realized by the monitoring master station include: serving as the monitoring and management center of the entire charging monitoring system, completing the collection and display of all charger information, the control and management of the charger, as well as the storage, management and statistics of the data of the entire charging monitoring system;

The functions realized by the power supply monitoring system include: real-time collection and recording of power supply system operation information, monitoring and controlling power supply conditions, power quality, switch status, equipment safety, etc., to ensure safe power supply to charging stations.

The monitoring main station and power supply monitoring system are implemented using an industrial computer, with the focus on software functions.

(2) Charger

A cRIO device is used as a semi-physical model of the charger system to simulate various functions of the charger, including controlling voltage output, current output, communicating with the battery system, and accepting monitoring and control from the monitoring master station.

The NI C Series platform includes more than 50 NI modules and more than 50 third-party modules with various types, including analog input, analog output, digital input, counter/timer, digital output and pulse generation, CAN communication, and serial communication (including RS232 and RS485).

(3) Battery system

The debugging process requires a standard electric vehicle battery system, which communicates with the charger in accordance with the requirements of the "Communication Protocol between Electric Vehicle Battery Management System and Off-board Charger". This part uses a cRIO device as a semi-physical model of the standard power system.

According to the above module division, after successful debugging, the prototype release stage is entered. The monitoring system software is developed using LabVIEW, and the LabVIEW development system has multiple versions such as Windows version, MAC OS version and Linus version, thus supporting the release on multiple operating systems.

After the communication functions and control algorithms of the charger and battery system are verified, the prototype platform can be used directly as a release platform to save release time and get to market faster; it can also be released to other platforms, such as the more cost-effective Single-Board RIO platform, without modifying the code.

Summarize

As part of the smart grid, charging electric vehicles is a difficult problem, because charging a car requires a large amount of current and a high-power power supply, and the harmonics generated are a great test for the safety of the power grid and the quality of power. There are also intelligent functions such as electronic monitoring, charger monitoring, billing and metering that need to be solved. If electric vehicles, especially pure electric vehicles, want to become mainstream, the first condition is to have convenient charging outlets. Charging stations will replace the role played by gas stations and gas stations in the near future and will be everywhere in people's lives. Shanghai Juxing Instruments provides solutions for the construction and development of charging equipment and charging facilities based on the NI LabVIEW software platform and cRIO hardware platform to help the development of China's electric vehicle industry.