G3-PLC technology solves the challenge of intelligent charging of electric vehicles

Abstract: This article analyzes the standard requirements for reliable communication between electric vehicles (EV) and electric vehicle supply equipment (EVSE). Data shows that the G3-PLC system fully meets the communication standards of the automotive and power industries. The G3-PLC solution, which has been tested and verified around the world, is the best low-frequency communication solution.

Electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) are forming an unprecedented and vibrant mobile electricity consumption market, and the relationship between electricity providers (power companies) and car owners is becoming increasingly clear. Many power companies have or are planning to provide special rate standards for EV users, including fixed monthly rates.

EVs have injected new vitality and demand into the electricity market. In fact, a mutually dependent relationship between EVs and energy providers has begun to take shape. Since EVs have a large energy storage capacity, typically 10kVH, they need to absorb 80A or even more current within a few hours. This adds significant pressure to grid equipment, especially for low-voltage transformers, which may overheat or even fail when supplying power to users' homes. In addition, the electric energy stored in EVs can also generate current backflow and deliver electricity to the grid to solve the power demand during peak power supply periods and avoid starting high-carbon emission diesel generators.

To establish this new interactive relationship, EVs and energy providers must communicate with each other. Power companies must be able to identify each car, and two-way communication is needed to measure the flow of power and power consumption. To meet this new market demand, various standards organizations, including the Society of Automotive Engineers (SAE), the International Organization for Standardization (ISO), and the International Electrotechnical Commission (IEC), have begun to develop communication standards for connecting EVs and charging stations (called electric vehicle supply units, EVSE). Integrating this safe and reliable two-way communication capability into the current power supply system involves many key issues. At the same time, as EV charging becomes a key industry demand, the new standard G3-PLC for smart grids has emerged as a leading technology for managing grid energy using power line communications.

This article analyzes the key requirements for reliable EV-EVSE communication, and the data shows that the G3-PLC system fully meets the new standards of the automotive and power industries. The G3-PLC solution, which has been tested and verified around the world, is the best low-frequency communication solution.

EV-EVSE Communication Standards

Over the past three years, automakers have investigated and tested a variety of EV-EVSE communication solutions. Recently, the Automotive Alliance has also locked its test results to two power line communication (PLC) solutions, and focused on G3-PLC as a low-frequency communication option. A viable communication solution faces many challenges, and designers are actively exploring any feasible solutions.

The key principles that the communication plan needs to follow are:

●Reliability – reliable data communications and components that meet automotive-grade requirements

●Meet EMC, joint interference and crosstalk limits

●Complies with global power line regulations

●Works via control line

●Works on AC or DC grid

●Provide secure networking support for energy management systems

In addition, automotive solutions bring special challenges to IC designers and manufacturers. ICs must be able to withstand harsh operating environments, must work reliably for 10 to 20 years, and meet automotive-related certification/quality assurance system requirements.

G3-PLC——The best choice for EV-EVSE communication technology

For some time, while the automotive industry is investigating, the power industry has also been developing high-reliability G3-PLC solutions with a service life of up to 10 years. These efforts have been supported by the world's largest power companies, including Electricité de France (EDF). G3-PLC power line modems are now available that can operate in harsh environments with negative signal-to-noise ratios (SNR). The importance of G3-PLC technology cannot be overstated, and it has become the key to ensuring reliable communication in any EV-EVSE condition.

The results of an independent DC charging trial funded by the U.S. Department of Energy in 2009 demonstrated the difficulties faced by EV-EVSE communications. The test results showed that Maxim's G3-PLC power line modem has highly reliable communication capabilities and can adapt to any operating conditions.

Noisy charging cable

Most stand-alone PLC solutions operate at lower currents, and G3-PLC is the only PLC system that can achieve reliable communication at 250A. Test data (Figure 1) shows that the noise can be 20dB stronger than the signal, or even higher; in addition, the noise frequency generated by the switching power supply is also different, depending on the specific switching power supply used. The G3-PLC system uses proprietary technologies to cope with harsh environmental conditions, including reliable operating mode (robo mode), adaptive frequency mapping, two-level error correction, and two-dimensional comb filtering. These features are detailed in IEEE ISPLC literature and verified by field tests. G3-PLC can achieve reliable data communication across transformers.

EMC suppression

Before the introduction of the G3-PLC transceiver, electromagnetic compatibility (EMC) has always been a major obstacle to the use of PLC for outdoor communications. However, since the G3-PLC system operates at a lower frequency (below 500kHz) and is designed for global smart grids, it has overcome the EMC problem. In fact, preliminary tests have shown that in the low-frequency band (500kHz), the EMC level is lower than the limit threshold of CISPR-25, and subsequent large-scale tests have also proved this point.

Joint Interference and Crosstalk

Typically, a charging station will charge multiple electric vehicles arranged in parallel. Once a communication error occurs, it will cause billing errors. Therefore, joint interference and crosstalk become the main concerns of EV-EVSE networks. The automotive industry initially considered using wireless communication solutions for this application, but it turned out that this solution could not guarantee reliable joint charging.

The PLC ensures that the EV being charged is correctly billed, using G3-PLC technology to solve this problem. When the EVSE switch is open, no communication is possible (Figure 2), ensuring that no communication can be made through open contacts or between charging lines in an EVSE with multiple charging lines. This functionality was further confirmed in a recent ISO 15118 PT4 test, in which the G3-PLC signal was increased to 10 times the normal operating level to introduce crosstalk. No crosstalk was detected under nominal conditions or even noisier operating conditions.

Figure 2. With G3-PLC, the transmit and receive signals indicate no communication between open contacts. Globalization is a key goal for automakers, and G3-PLC systems have been extensively tested in multiple regions around the world, operating in licensed bands from 10kHz to 500kHz authorized by various countries. To support regional differences in licensed bands, the Maxim G3-PLC solution provides programmable functions to meet the regulations of the deployment area. As a result, in the European power company test, the G3-PLC system was programmed in the CENELEC A band (up to 95kHz); in the US test, G3-PLC was set in the FCC band (up to 490kHz), and in Japan, it was set in the ARIB band (up to 450kHz).

Working on control line

When operating on the control line, the G3-PLC transceiver needs to overcome more design challenges. To meet the SAE J1772 specification, two key factors need to be considered when operating on the control line: ultra-low voltage and coupling issues to avoid PWM interference. Given the rugged nature of the G3-PLC system, operating at low voltage (and low current) is not a problem. Figure 3 shows that it can operate normally below 500mV without packet loss and without the need for retransmission.

Figure 3. G3-PLC signal waveform with inductive coupling on the control line, indicating that it supports PWM and PLC communication

In addition, care must be taken to avoid overloading the PWM signal (which adversely affects the slew rate) and to avoid PWM harmonics from the 1kHz, 12V signal. To ensure that the PWM signal frequency band does not overlap with the G3-PLC transmission frequency band, the G3-PLC system is set to operate above 150kHz. To ensure that the PWM slew rate is within the system limits, inductive coupling is preferred over capacitive coupling.

Versatility brings more possibilities

As an AC power solution, the G3-PLC solution has been extensively tested by many power companies around the world. The test results sponsored by SAE show that the G3-PLC system can send tens of millions of automotive power consumption data with zero bit errors. Since the G3-PLC system can work on powered and non-powered lines (AC grid, control line, CAN or any medium), it can provide reliable reliability.

The G3-PLC solution attaches great importance to the Advanced Meter Infrastructure (AMI), opening a new door for EV-EVSE communication on the AC grid: the G3-PLC system can communicate directly with the meter. Figure 4 shows the complete ecosystem that G3-PLC can support. It is expected that the EVSE in the home will have an independent, dedicated circuit breaker to provide a direct path to the external power circuit breaker to avoid the impact of phase difference.

Figure 4. G3-PLC communication routing from EV to power company

Some power companies have already added IPv6 addressing to G3-PLC systems before car manufacturers have asked for it. In fact, as Stephen Shankland wrote in an article in ZDNet, IPv4 addresses are almost exhausted, so supporting IPv6 has become a top priority. The G3-PLC solution uses a 6LowPAN compression solution to ensure support for true IPv6 addressing. With G3-PLC using true IPv6 networking, PHY and MAC non-deterministic energy management solutions can switch seamlessly on the network.