What is an EMS?
An Energy management system (EMS) is a technical solution for monitoring and controlling the flow of electrical energy. It coordinates generators, battery storage systems, consumers and metering devices on the basis of current readings, threshold values and operating strategies.
EMS at a glance
- An EMS collects measurement and status data from the system and uses this to calculate permissible setpoints for controllable components.
- Typical tasks include optimising self-consumption, peak shaving, feed-in limitation, zero feed-in and the processing of external schedules or setpoints.
- Reliable control requires suitable measuring instruments, up-to-date data, stable communication and controllable devices.
- An EMS does not replace technical protection systems. It does not assume the energy-market role of a direct marketer.
How does an EMS work?
The control system begins by cyclically recording measured values. The grid connection point is particularly important, as this is where the grid consumption or grid feed-in for the entire customer’s installation is measured. In addition, the EMS can read data from PV inverters, battery systems, charging points, generators and controllable loads. This includes power, voltage, current, frequency, state of charge, device availability and error codes.
Depending on the system configuration, the EMS can check the recorded data for timeliness, plausibility and completeness. The control logic then calculates setpoints, authorisations or restrictions. In doing so, it takes into account, amongst other things, connection and feed-in limits, device power, minimum and maximum SOC values, current availability, device status and project-specific priorities. Higher-level protection and safety devices always take precedence.
When regulating at the grid connection point, the EMS continuously compares the measured value with a setpoint or limit value. In the event of a deviation, it can, for example, reduce PV output, charge or discharge a battery, and limit flexible loads. Depending on the system design, the EMS can check external specifications from grid operators, direct sellers or third-party platforms locally for plausibility and technical feasibility, and distribute them within the permissible operating limits.
Depending on the device and project, data exchange may utilise protocols such as Modbus TCP, Modbus RTU, REST APIs, MQTT and OCPP, as well as digital inputs and outputs. Many EMS systems also store measurement history, alarms, communication statuses and issued control commands for monitoring and fault analysis.
Typical use cases for an EMS
- PV and battery systems: Surplus PV power can initially be stored in the battery before the PV system is curtailed. During periods of high consumption, the battery can be discharged within its operating limits.
- C&I sites: For peak shaving, the EMS limits peak loads by controlling a battery system or flexible loads. It can also distribute a limited connected load across several areas of the site.
- Charging infrastructure: The EMS coordinates charging points with PV, batteries and other site loads to ensure that the available connected load is not exceeded.
- Hybrid and market-integrated systems: In systems incorporating PV, battery systems, generators or external schedules, the EMS coordinates local operational priorities with the technical requirements of higher-level systems.
Benefits, limitations and technical requirements
An EMS can make energy flows more transparent, increase self-consumption, reduce peak loads and make better use of grid connection capacity. It can also implement external setpoints and document control processes. The actual benefits depend on the system structure, the load profile, the available flexibility and the chosen operating strategy.
An EMS can only perform functions supported by the connected devices and interfaces. Communication failures, outdated measurement values, device faults, SOC limits or slow response times can restrict the implementation of setpoints. Protection and safety devices always take precedence.
In particular, a suitable measurement concept, correctly positioned measuring devices, update rates appropriate to the control dynamics, stable communication channels and controllable plant components are required. Threshold values, priorities and fault responses must be defined and tested on a project-specific basis.
How does EcoPhi implement EMS functions?
EcoPhi provides a local EMS and monitoring layer comprising hardware and a platform. It can consolidate measurement data from the grid connection point and individual system components, calculate setpoints, control PV and battery systems, process external specifications, and visualise operational data, alarms and control processes. Communication statuses and the timeliness of relevant measurement data can be monitored and displayed within the platform.
The specific scope of functions depends on the devices used, the available interfaces and the required control strategy. EcoPhi can serve as a technical link to direct marketers, SCADA systems or other third-party platforms, but does not assume their role in energy management.
Conclusion: The technical coordination level of the power plant
An EMS combines measurement, data processing and system control. It coordinates PV systems, battery systems, loads and external specifications within defined technical limits. A suitable measurement concept, stable communication, compatible interfaces and clearly defined control strategies are crucial for reliable operation.
FAQ
What is the difference between an EMS and a direct marketer / trader?
The direct marketer / trader is responsible for the energy-related marketing of energy or flexibility. An EMS can support the technical implementation by receiving schedules or setpoints, checking them locally for technical feasibility depending on the system design, and passing them on to controllable plant components.
What types of systems can an EMS control?
Depending on the available interfaces, an EMS can control, amongst other things, PV inverters, battery systems, charging infrastructure, generators and flexible loads. This requires that the devices support external control or the processing of the relevant setpoints.
Does an EMS still work in the event of a communication failure?
The response depends on the system architecture and on the project-specific safety and fault management concept. In the event of a failure of the external connection, locally implemented control systems may continue to operate, depending on the system architecture. If, on the other hand, communication with measuring instruments or controllable components fails, control is usually significantly restricted. In the event of missing, outdated or implausible data, the system must switch to a defined operating state in accordance with the specified fault response.