Modbus Gateway Enables Resilient Smart EV Charging Architecture
Summary
The integration of EV charging requires a hybrid communication architecture that leverages the distinct strengths of Modbus and OCPP. This model uses Modbus as the resilient “field layer” protocol for real-time, local data acquisition from on-site energy assets, operating independently of internet connectivity. Concurrently, OCPP serves as the “application layer,” managing the cloud-based user service layer, including authorization, billing, and standardized smart charging commands. The key to this implementation is a protocol gateway that can convert between the two domains, enabling advanced applications like Dynamic Load Management (DLM). This architecture provides a layered security model, confining insecure Modbus traffic to a protected local network while leveraging OCPP’s robust encryption for internet-facing communication, creating a resilient and future-proof solution.
▶ Four Communication Architectures
Architecture 1: OCPP Central System Mode. The OCPP central system directly controls charging operations, order management, and smart charging at charging points via a Modbus gateway. For charging points that support the OCPP protocol, the gateway can be omitted. Most public charging stations use this communication architecture.
Architecture 2: BMS Central System Model. In this model, the local building management system (BMS) directly controls charging operations at the charging points and is responsible for intelligent charging and load management. This model is ideal for critical infrastructure such as logistics warehouses.
Architecture 3: Hybrid Mode 1. Basing on Architecture 2, this approach connects OCPP charging points and the OCPP central system via a Modbus gateway, expanding the range of charging points available and enabling remote management of system status and user orders.
Architecture 4: Hybrid Mode 2. Basing on Architecture 2, this approach connects to the OCPP central system via a Modbus gateway. This also avoids the potential for single-point gateway failure in Hybrid Mode 1, which could disrupt communication across the entire system.
▶ Horizontal comparison of 4 architectures
▶ The Hybrid Architecture: Complementary Roles and Integration
A robust smart charging system uses Modbus and OCPP in complementary layers. Modbus acts as the local workhorse, providing reliable data from on-site energy assets like utility meters and solar inverters without needing an internet connection. OCPP functions as the cloud commander, managing the user-facing charging service (authorization, billing) and sending high-level smart charging commands from a remote Central Station Management System (CSMS).
The essential component bridging these two domains is the protocol gateway, which translates data and commands. This enables two different priority operation models.
▶ Use Case Spotlight: Dynamic Load Management (DLM)
Dynamic Load Management (DLM) is the key application of the hybrid architecture. It intelligently adjusts power to EV chargers to ensure a facility’s total consumption never exceeds its capacity, preventing overloads and avoiding costly electrical upgrades. In the hybrid model, a local controller uses Modbus to continuously poll the building’s main power meter for real-time load data. It then calculates the available power budget and send commands to the chargers, limiting their consumption accordingly. This entire control loop runs locally, providing a rapid and resilient response to changing energy demands.
▶ Considerations in the Hybrid Model
The two hybrid models provide a layered security strategy. Modbus, an older protocol, has no native security features like encryption or authentication and transmits data in plain text. In contrast, modern OCPP versions mandate TLS encryption and support robust certificate-based authentication. The hybrid architecture mitigates Modbus’s weakness by confining its use to a physically secure and logically isolated local network. All external communication over the internet is handled by the secure OCPP protocol, creating a defense-in-depth security posture. At the same time, hybrid model 2 can also prevent the entire communication system from being interrupted due to a single point failure of the gateway.
▶ Conclusion
By combining Modbus’s local resilience with OCPP’s cloud management capabilities through a Modbus protocol gateway, an efficient, scalable, and secure smart charging system is achieved.
Shenzhen WiseWish Technology Co., Ltd.’s WIS901 series Modbus protocol gateway is an ideal choice for implementing these hybrid systems:
- Conveniently implement Architecture 1 and Architecture 4 charging system
- Offers custom development based on the Modbus MAP of the customer’s devices
- Certified to EN18031 cybersecurity standards.