AVOIDING CONFUSION IN THE AC TO DC RECTIFIER MARKET

EVERYTHING ABOUT COMMUNICATIONS PROTOCOL CONVERTERS

Industrial AC-DC rectifier systems, whether SCR-based low-frequency or modular high-frequency types, convert alternating current (AC) to direct current (DC) to charge batteries and power industrial DC loads for telecommunications, data centers, and electrical substations.

These systems generate a wealth of operational data, such as voltage, current, temperature, battery state of charge, fault codes, and breaker status, which are transmitted via communication interfaces such as RS-485 or RS-232 and displayed on an integrated digital display. They also allow for external commands, such as shutting down the system in emergencies or changing the charging mode.

However, integrating this data into external systems, such as computer workstations or remote networks, creates confusion due to the variety of communication protocols required, depending on the region, application, or local culture, such as Modbus, SNMP, DNP3, IEC61850, and TCP/IP. This is the reason for writing this White Paper. Manufacturers offer protocol converters to facilitate this integration. However, users often face difficulties when trying to replicate the display's functionality on other devices. Then we want to make clear our role: Avoiding confusion in the AC to DC Rectifier market.

This post explains the differences between these communication protocols, reasons for choosing one over the other, confusion surrounding protocol names, the scope of protocol converters, and the responsibilities of manufacturers and users.

1. Communication Protocols in Industrial Rectifiers.

Industrial rectifiers use communication interfaces to transmit operational data and receive commands. The most common protocols and their characteristics are described below:

RS-485 and RS-232.

• Description: These are serial communication standards. RS-232 is ideal for short distances (up to 15 meters) and point-to-point connections, while RS-485 supports longer distances (up to 1200 meters) and multiple devices on a single line (multidrop topology).

• Use in rectifiers: Most rectifiers use RS-485 due to its robustness and ability to connect multiple devices. RS-232 is less common but is used in simpler applications.

• Example: A rectifier sends voltage and current data via RS-485 to a digital display or local monitoring system.

MODBUS.

• Description: This is a serial communication protocol widely used in industrial automation. It can operate over RS-485 (Modbus RTU) or TCP/IP networks (Modbus TCP). It defines how data is structured and transmitted between devices.

• Use in rectifiers: This is the most common protocol for rectifiers, allowing data such as battery charge status or fault codes to be transmitted simply and reliably.

• Advantages: It is easy to implement, compatible with many devices, and suitable for general industrial applications.

TCP/IP.

• Description: This is the set of protocols that underpins the Internet, allowing communication between devices on IP networks. It can carry protocols such as Modbus TCP or SNMP.

• Use in rectifiers: Some modern rectifiers have Ethernet connectivity and use Modbus TCP to send data to remote systems.

• Advantages: Allows long-distance communication and scalability, ideal for integrating rectifiers into corporate networks or SCADA systems.

SNMP (Simple Network Management Protocol).

• Description: This is a protocol for managing devices on IP networks, primarily used to monitor the status of equipment such as routers and servers.

• Use in rectifiers: Although not typical, some rectifiers can use SNMP to integrate with network management systems, reporting data such as system status.

• Advantages: It is useful in environments where rectifiers are part of a larger IT network.

DNP3 (Distributed Network Protocol 3).

• Description: This protocol is designed for the electrical industry, specifically for robust communications in harsh environments, such as substations.

• Use in rectifiers: It is used in energy applications where rectifiers are integrated into SCADA systems.

• Advantages: It is error-resistant and suitable for low-speed, high-reliability environments.

IEC61850.

• Description: This is an international standard for electrical substation automation, defining how intelligent electronic devices (IEDs) communicate with each other and with control systems.

• Use in rectifiers: It is relevant in substations where rectifiers are part of a more complex automation system.

• Advantages: It offers an advanced structure for communication in highly complex environments.

2. Differences between Protocols and Communication Needs.

Each protocol has a specific purpose and adapts to different needs:

MODBUS vs. IEC61850:

• MODBUS: It is lightweight, simple, and suitable for general industrial applications where direct communication between devices is required. For example, a rectifier can send current data to a local controller using Modbus RTU over RS-485.

• IEC61850: It is more complex and designed for electrical substations, where multiple intelligent devices must interoperate. It is ideal for environments where structured and detailed communication is required.

RS-485 vs. TCP/IP:

• RS-485: It is robust and suitable for industrial environments with electrical noise, but it is limited by physical distances and is not ideal for remote communication.

• TCP/IP: It allows communication over IP networks, which is useful for remote monitoring or integration with enterprise systems, but requires network infrastructure.

SNMP vs. DNP3:

• SNMP: Focuses on network management and is more common in IT environments, not industrial rectifiers.

• DNP3: Is specific to the energy industry, offering robustness for critical applications such as substations.

Reasons for choosing a protocol:

• Region and local standards: In Europe, IEC61850 is common in substations due to its adoption in the energy industry. In North America, DNP3 is more prevalent due to its historical use in SCADA systems.

• Specific application: For simple local monitoring, Modbus is sufficient. For complex substations, IEC61850 or DNP3 is preferable.

• Existing infrastructure: If a user already has a DNP3-based SCADA system, it makes sense to choose a rectifier compatible with that protocol or use a converter.

3. Confusion over Protocol Names.

Confusion arises because some terms are used generically or overlap:

• MODBUS: Sometimes used to refer to any serial communication, it is a specific protocol that structures data over RS-485 or TCP/IP.

• TCP/IP: Not a single protocol, but a suite of protocols that includes applications such as Modbus TCP or SNMP. Users may confuse it with an application protocol.

• IEC61850 vs. DNP3: Both are standards for the power industry, but IEC61850 is more modern and geared toward substations, while DNP3 is older but still widely used in North America.

This confusion is compounded when users attempt to replicate the rectifier's digital display functionality on external systems, such as workstations or remote networks, without understanding the protocol limitations or the need for converters.

4. Scope of Protocol Converters.

Protocol converters are devices that translate data from one protocol to another, enabling interoperability between systems. Examples include:

• RS-485 (Modbus RTU) to IEC61850: Allows a Modbus-enabled rectifier to be integrated into a substation system using IEC61850.

• RS-485 to SNMP: Enables communication with grid management systems.

• RS-485 to DNP3: Facilitates integration with SCADA systems in the energy industry.

Scope:

• Converters convert data between protocols, ensuring that rectifier information (such as voltage or charge status) is accessible in the required format.

• They can be physical devices or software embedded in the rectifier or an external system.

• Their configuration may require specific settings, such as data mapping or defining communication points.

Limitations:

• Converters cannot generate data that the rectifier does not provide. For example, if the rectifier doesn't measure temperature, the converter can't measure it.

• The quality of the conversion depends on compatibility between the protocols and correct configuration by the user.

5. Manufacturer and User Responsibilities.

Manufacturer's Responsibilities:

• Data Provision: Ensure that operating data (voltage, current, temperature, etc.) is available through interfaces such as RS-485 or RS-232, typically using Modbus.

• Digital Display: Provide a display that displays system data, with detailed graphics if necessary.

• Protocol Converters: Offer converters (or support for them) that allow integration with protocols such as IEC61850, DNP3, or SNMP, if the user requires it.

• Documentation: Provide clear manuals on how to access data and use the converters, including register maps for Modbus or other protocols.

User Responsibilities:

• Protocol Selection: Choose the appropriate protocol based on your system's needs (e.g., Modbus for local monitoring, IEC61850 for substations).

• Converter Configuration: Configure protocol converters so that rectifier data is compatible with external systems.

• External Integration: Implement monitoring or control systems (such as workstations or SCADA) that use the data provided by the rectifier.

• Remote Data Management: If data is needed on remote networks or in other countries, the user must configure the network infrastructure (e.g., using TCP/IP) and ensure communication security.

6. Practical Example.

Imagine an industrial rectifier in a substation that uses RS-485 with Modbus RTU to transmit data such as output voltage and battery charge status.

The user needs to integrate this data into a SCADA system that uses DNP3.

The manufacturer provides a Modbus RTU to DNP3 converter, which translates the rectifier data into the required format.

The user configures the converter, maps the relevant data (such as voltage), and integrates it into the SCADA system. If the user wants to monitor the data from another country, they can use Modbus TCP over a TCP/IP network, but they must implement the network infrastructure and ensure security.

7. Conclusions.

• Industrial rectifier systems are essential for critical applications, and their effective communication depends on protocols such as RS-485, RS-232, Modbus, SNMP, DNP3, and IEC61850.

• The choice of protocol depends on the application, region, and existing systems, which can be confusing when users try to integrate the data into external systems.

• Protocol converters are key tools for resolving these differences, but they require user configuration.

• Manufacturers are responsible for providing accurate data and appropriate converters, while users must manage the integration and use of this data in their systems.

• With a clear understanding of the protocols and proper configuration, rectifiers can be effectively integrated into any industrial environment. And that's part of our services.

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