Development of intelligent HEV / EV infrastructure chargers around single processors


With the increase in the proportion of electric vehicles driving on the road, the demand for charging stations has also exploded. Although there are many charging stations for free use in some restaurants and shopping centers, the demand for "paid charging stations" in urban and rural areas is also increasing. These charging stations allow electric vehicles to achieve longer travel distances. This requires higher technology to achieve intra-system communication, including near field communication (NFC) technology for mobile payment, Wi-Fi, Ethernet and power line communication (PLC) technology for payment processing, and the use of advanced electricity meters And auxiliary control functions. After the emergence of the C2000 ™ C28x digital signal processor (DSP) + ARM® Cortex ™ -M3 device, we can now integrate all these functions into a single low-cost processor.

Integrated communication

Today, more and more people start to use electric vehicles, whether it is motorcycles, special vehicles or public transportation that they take daily. It has led to an increase in demand for charging stations, especially in helping these vehicles increase driving distance. Although many places offer free charging services, paid charging stations are also necessary. There are many charging stations in the city, and their appearance and working methods are similar to parking meters, but there is an additional charging line to connect electric vehicles.

So far, there are three common charging stations (by level). Levels 1 and 2 are common "fuel gauge" AC power sources that use the on-board charging function of electric vehicles. Now, the third common charging station (currently not called a level) is a DC "fast charger", which bypasses the power factor correction (PFC) on the electric vehicle board and provides 400V DC power directly to the battery charging stage. The power levels and power levels of all three systems are different, but all need to measure how much electricity is used and explain the amount of charge to consumers, and all require communication with the back-end network.

For credit card charging, mobile user mobile phone charging and even cash transaction processing, it is necessary to communicate with multiple back-end networks. For designers, they need it to achieve the flexibility of their architecture. Using TI's C2000 dual-core microcontroller and other processors, we can now have the flexibility of PLC, Wi-Fi, 10/100 Ethernet and NFC communication in a single processor, it can also handle meter functions, housekeeping management Even the power level control within the system. By integrating everything into a single controller, we can reduce board space, bill of materials costs, and integrate advanced protection features, all of which are integrated into a single controller.

Advantages of real-time C2000 DSP + ARM

The C2000 DSP + ARM series microcontrollers, which start at only $ 7, are a new type of mixed-signal, multi-core processor device and belong to TI MCU series devices. It has the performance advantages of the 32-bit processing of the C28x DSP core, while combining the industry standard ARM Cortex-M3 core flexibility to provide designers with unmatched flexibility in mixed-signal, communication systems. Developers can also take advantage of the analog processing capabilities of these devices, which have up to 24 ADC channels, 6 integrated analog comparators, and industry-standard communication protocols, including USB, 10/100 Ethernet, I2C, and SPI interfaces, so Other radio technologies communicate to provide a complete system in one processor. Integrated memory, power supply, and monitoring peripheral devices are also integrated into the device, further reducing the need for external components.

Brief introduction of C2000 DSP + ARM microcontroller:

• Dual processor technology—independent C28x 32-bit control core and ARM Cortex-M3 communication core

• SRAM embedded flash memory up to 1.5MB and 232KB for application memory and program memory

• Integrated analog peripherals, including 24 12-bit ADC channels, 6 analog comparators and 27PWM output channels

• Integrated communications, including USB, 10/100 Ethernet, I2C, SPI and CAN peripheral devices

• Single power supply operation

• Integrated power-on reset and power-off reset function

The basis of all electric meter systems does not exceed the analog processing capacity of the main processing unit. Using the analog function of the C2000 dual-core device, we can easily achieve the required voltage, and the current monitoring function required for single-phase and three-phase AC measurement, and can monitor the output level of higher output DC-type systems. To simplify some of the diagrams in this article, we decompose the system into 2 sub-sections:

1. The monitored power supply itself

2. The low-voltage communication end of the system

Since we are dealing with low and high voltage systems, we must also consider the isolation requirements between high and low voltage systems. Although C2000 dual-core devices can handle power-level control, this article focuses only on higher-level measurements and communications.

C2000 dual-core microcontroller for electric meter application

As mentioned earlier, electric vehicle chargers are currently divided into three categories: Level 1 and Level 2 represent AC charging, and Level 3 is DC fast charging. In Level 1 and Level 2 systems, the charging station architecture looks very similar to the standard electricity meter application for most smart grid applications. This meter is simply connected to a single-phase or three-phase AC power supply (public power grid), and there is no power control stage in the system. It works exactly the same as a home electric meter. It monitors the current passing through the system, but only increases the communication with the charging electric vehicle. As a payment gateway, it may also include a safe disconnect function. Both Level 1 and Level 2 chargers use an electric on-board charging system, which includes a power factor correction boost level and a high-voltage DC charging circuit. The level 1 charger is based on the standard 120 / 240V AC level and provides a maximum charging current of 16 amps. Level 2 charging can use 240V AC or 480V three-phase AC, but both are limited to 32A. In addition, in the case of level 1 or level 2, the charger only serves as a meter function between the general power grid and the electric vehicle receiving the charge, and there is no energy conversion level.

Figure 1 Simplified signal chain for "smart" fixed charging stations

Figure 1 Simplified signal chain for "smart" fixed charging stations

The DC fast charging system works in a different way. It converts the AC power voltage level to a boosted DC level and can provide up to 400 amps of current. Although Class 1 or Class 2 chargers can charge ordinary electric vehicles within 4 to 8 hours, DC booster chargers can complete the same charging work within 20 to 30 minutes. The power levels of Level 1 and Level 2 are very different compared to Level 3 chargers, but this meter application is often used for all three chargers because the measurement input is always AC power and is in front of all PFC levels.

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