Electric cars (EVs) are indeed revolutionizing private transportation, steering us towards a more environmentally friendly tomorrow. With an increasing number of people adopting EVs, the supporting infrastructure that is the charging points, demand attention. It is vital that these systems are safe, reliable, and operate in cohesion with each other regardless of the model of the car or charging location.

And that is where the IEC 61851 steps in. It is the world’s rulebook for conductive EV charging systems. The International Electrotechnical Commission (IEC) crafted it, and it sets forth road rules for charging a car. Everything from how the equipment should be charged, connected, to the safety checks that need to be performed, and the communication between car and charger, all of this is clearly set out in the IEC 61581.

Being acquainted with the details of this standard brings the technology behind electric mobility into focus. There are several parts to the IEC 61851 family, each dealing with various aspects of the EV charging equation to make performance consistent and safe.

Breaking Down the Four EV Charging Modes

The IEC 61851 has 4 broad categories of EV charging based on the environments, power levels, and safety types. These modes are used to divide the numerous types of charging into working cohesively and safely in the process.

Mode 1: This is the first mode of charging. It is a simple mode to charge an EV with AC power supply where vehicles are connected using a common wall plug with the assistance of a regular charging cable. There is no safety device in this mode and hence it is used mostly for a low power-rating, mostly small electric vehicles like scooters and bicycles3. Typically, it is installed on light electric vehicles like scooters and bicycles that have a low power-rating3. Due to the absence of top-end safety provisions, Mode 1 is prohibited in most nations for normal EV charging 1. Since there is little communication between the EV and the charging stations, overcharging and electrical hazard issues are real dangers and Mode 1 is less suitable for the high-power demands of most electric vehicles.

Mode 2: Mode 2 uses an odd charging cable with an integrated control box (an IC-CPD). It is still plugged into a standard AC outlet, but this box prevents surplus current or electrical breakdowns. This mode is better than Mode 1 and is primarily accepted as a domestic charging technique, it provides in-cable and a protection device with an overload protection too.

Mode 3: This charging mode has its own Electric Vehicle Supply Equipment (EVSE), i.e., it is a charging station offering a greater level of safety and more control 1. Single-phase and three-phase AC supply are both supported by this mode 3. It also possesses Residual Current Device (RCD) protection that can detect current leakage and is a major contributor to functional safety and offers bidirectional communication facilities between EV and EVSE 1. It is typically applied both in domestic and commercial use because of all its other functionalities of safety. It provides higher levels of power for faster charging than Modes 1 and 2 1.

Mode 4: This is commonly recognized for its speed of charging and the advanced method it uses. An expert DC charger (EVSE) brings direct current right to the automobile’s battery. The process bypasses the car’s integral charger completely, allowing very speedy power-ups. This mode is most often reserved for high-level public fast-charging locations or business centers. However, the payback is huge: tremendous power. This means that the batteries charge very quickly compared to any other means. For individuals who travel long distances by driving, or drive work vehicles such as taxis and buses, where the charge must be fast, this kind of quick charging is enormously important.

For ease of comparison, the key characteristics of these charging modes are enumerated in the table below:

Table 1: Summary of IEC 61851 Charging Modes

Understanding the Basics: Control Pilot and Proximity Pilot

The reliability and safety of a mode is established by how the EV and EVSE communicate. Two IEC 61851 signals are used for this, i.e., the Control Pilot and Proximity Pilot (PP)4.

The Control Pilot (CP) signal is the primary communication channel, enabling a dialogue between the charger and the car to charge in a controlled and secure way. The EVSE transmits a 1 kHz ±12 V Pulse Width Modulation (PWM) signal on the CP line to inform the EV of the maximum charging current it can receive 4. For instance, when an EV is plugged in but not yet ready to be charged (State B), it signals this by a particular resistance, inducing a particular voltage level on the CP line (around +9V) 4. When the EV is ready to receive energy (State C), it places a different resistance, changing the CP voltage to around +6V 4. The presence of around +3V on the control pilot line shows State D, a phase where charging initiation is feasible, subject to proper ventilation. This continuous exchange of data points between the charger and the electric car facilitates mutual understanding of each other’s status and capability and, in the process, provides room for a frictionless and flawless charging regime.

The Proximity Pilot (PP) message has the insidiously subtle yet no less valuable task of preventing physical contact of the charging cord. Its functional sensitivity is built on the category of the connector. With Type 1 interfaces, the PP signal is a sentinel that checks not only for the existence of the EV, but most critically, that the connector is correctly locked. To prevent any unwanted interruption of energy transfer and protection from resultant hazards, the functional logic must require that the electrical power delivery initiates only when a stable interface is confirmed. For Type 2 connectors with no auxiliary switching mechanism, the Proximity Pilot signal provides a unique interpretation of the peak amperage capability of the cable as a resistive read. This sophisticated approach enables the charging point to dynamically tailor the supply of its current in real-time, synchronizing the cable’s own operating limits, thus removing cables out of the anticipated energy levels, and enhancing the overall safety system 4.

In response to this, the various states of the Control Pilot signal, as reflected by varying voltage amplitudes, are outlined below:

Table 2: Control Pilot Signal States and Voltages

Furthermore, the PWM duty cycle of the CP signal is proportional to the maximum charge current of the EVSE. The following example demonstrates this proportionality:

Table 3: PWM Duty Cycle and Charging Current

A Series of Operational Transitions: Charging Sequence

To truly feel the delicate mechanics controlling how electric cars recharge their juice, as specified in IEC 61851, visualize a smooth slide through a series of separate but linked operating phases. It is more rational to visualize the energy flowing in incrementally, instead of on and off. Gradually, adjustments are made to get to an equilibrium. There is a transfer of power from the power source to the car during recharging. All along, from the start to the finish, the process determines the way the energy flows. The charging begins in the Initial State (A1, A2) when the car is not yet connected to the EVSE 5. It can be in an unprepared state (A1) or a prepared state to supply energy (A2). Insertion of the charging cable is what triggers a transition from the Connected, Not Ready (B1) state. B1 sub-state means that the car is plugged in, but the EV and EVSE are not yet ready to go ahead and charge. If EVSE can supply energy, it moves to sub-state B2. It moves to the Initial State (A1) from B1 when pulling out charging cable 5.

If a vehicle is ready to be supplied with energy, it notifies the charger. This makes it move to either of them Connected, Ready states, like C1, C2, D1, D2. C1 and C2 denote car ready charge, no air required. C2, the charger is ready also to provide power. The same as D1 and D2 but with charging area ventilation for the EV. Readiness of EVSE governs the changeover from the ‘1’ to the ‘2’ sub-states (i.e., C1 to C2) 5. On a need for ventilation by EV, changeover from C2 to D2. In these ‘C’ and ‘D’ states, energy is transferred. A vehicle disconnect request will trigger a return to ‘B’ states (B1 or B2) 5. Upon finishing charging or when the user disconnects the vehicle, the system returns to the ‘A’ states (A1 or A2) from C2 or D2.

If the charger is at fault, or the car connection is lost, then it goes to Fault or Error points, i.e., E, F. That ensures that there is no power when insecure. Timing in such changes is extremely critical. Synchrony between the car and charger so that they work harmoniously and ensure security is vital.

Prioritizing Safety Requirements in IEC 61851:

Safety is important in IEC 61851. The standard ensures that there are no electrical problems that might hurt people and or affect the chargers. It has a few requirements to adhere to for safety.

One of the most important requirements is earthing. In Mode 3 charge, the wire to the ground must always be connected and should never be turned off. This provides dirty electricity with a safe route to escape. Also, there must be a way to dissipate excess power. This stops chargers and vehicles from being damaged by excess electricity flow.

Residual Current Devices (RCDs) must be used for current leakage detection that could pose the risk of an electric shock. The standard only recommends Type A or Type B RCDs for AC charging 2. One of the major reforms of 2017 to IEC 61851-1 necessitated the detection of smooth DC fault currents, which is relevant considering the increasing use of DC charging. While using DC chargers, one surely needs to avoid leaks from high-power lines 2.

In the event that there is serious trouble, the interrupt button must be used, to disconnect power for a brief time, to ensure safety. The plugs and wires must be strong, and have good insulation, for prolonged operation and for a secure connection. The IEC 61851 works together with other safety standards too, like the ISO 26262, for safety of motor vehicles, and IEC 61508, for electrical safety. These guidelines hold a fundamental position when considering the computer components in chargers and vehicles.

The above table illustrates the main safety requirements regarding the various charging modes:

Table 4: Key Safety Requirements by Charging Mode

Connecting the Dots: Understanding EV Charging Connectors

The physical interface between an electric vehicle and a charging station is offered by connectors, and they must be standardized to make them compatible and usable. The IEC 61851 is supplemented by other standards, notably the IEC 62196 series, that specifically state the requirements and tests for plugs, socket-outlets, vehicle connectors, and vehicle inlets for conductive charging 1. The standards have the consequence that any plug from a charging station can safely and reliably connect to the inlet of a suitable EV regardless of the manufacturer and the location.

There are several standard connector types in the world that usually have regional emphasis. Type 1 connectors (SAE J1772) are widely used in North America and Japan, primarily for single-phase AC charging 1. On the continent of Europe, the Type 2 connector (Mennekes) is the standard for AC charging and serves as the basis for the Combined Charging System (CCS) Combo 2 connector 1. The CCS connectors, Combo 1 (North America, South Korea) and Combo 2 (Europe, Oceania) 1 combine AC and DC fast charge in a single plug. In Japan, it was CHAdeMO biased for a DC fast charge. In China, the GB/T for AC and DC are used. The NACS (Tesla plug), is now more common in North America, for AC and DC too. These plugs connect to IEC 61851, and turn cars into plug-ins, anywhere. Plugs get smarter, as they move towards delivering more power and becoming less complicated.

Table 5: Common EV Charging Connector Types

Staying Updated: Recent Developments in IEC 61851

IEC 61851 is often updated and changed. This ensures that it keeps pace with the new EV tech and charging needs. All the improvements, towards DC charging, which aid in faster charging and extended journeys. Standards, like the IEC 61851-23 and IEC 61851-24, provide information on DC stations and digital communications between chargers and vehicles.

Moreover, newer versions of the IEC 61851 add two-way power, such as vehicle-to-grid to their list of requirements. This allows cars to send power back, potentially helping with grid stability. stability. Work is continuous on the standards to pave way for newer and better EV technology.

Software Development According to IEC 61851 Standards by eInfochips:

eInfochips’ charging products are extremely conformant to the international standards IEC 61851-1 and IEC 61851-21. The chargers designed by eInfochips’ are Type 2 connector compatible in full; these are employed for Mode 3 charging as per IEC 61851. Mode 3 charging, depends on a special charger, called the EVSE, provided by the AC power network. The charger has control and protective elements.

The software in such chargers is IEC 61851 compliant, to enable intelligent and safe charging processes. They also use communication protocols such as OCPP and Modbus TCP to exchange data with external systems. This enables smart capabilities. The software is utilized in controlling the usage of power, to render it efficient, a big consideration for Mode 3 chargers, which communicate both ways.

Safety is extremely important and the process includes many software checks and control safety functions. This additionally includes RCD, to avoid 6mA DC leakage, by the IEC standards. The software renders all charging safe by the IEC standards.

Conclusion: Empowering the Future of Electric Mobility

Overall, IEC 61851 is a cornerstone in electric vehicle charging installation. By providing a comprehensive set of worldwide guidelines, it not only renders EV charging safe and reliable, but also cooperative, anywhere on the planet. From prescribing easy charging, to specifying key communication needs and high-level safety needs, the IEC 61851 opens the door to frictionless charging for EV consumers. As the popularity of electric vehicles increases, continued innovation and compliance with standards like IEC 61851 will be essential in ensuring success.

Know More: Automotive Engineering 

References: 

1. https://en.wikipedia.org/wiki/IEC_61851
     
2. https://www.ledestube.com/understanding-global-standards-for-ev-charging-station-conduits/
    
3. https://www.evengineeringonline.com/what-is-the-iec-61851-1-standard-for-ev-charging/
    
4. https://www.hdt-electronic.com/en/faq/how-does-evse-work-what-are-control-pilot-and-proximity-contact-signals/
    
5. http://www.msi-automation.com/Download/jishujiaoliu/IEC61851-1-2010-%E6%8E%A7%E5%88%B6%E5%AF%BC%E5%BC%95%E7%94%B5%E8%B7%AF%
   E7%9B%B8%E5%85%B3%E5%86%85%E5%AE%B9.pdf