Four Capabilities and Four Remotes: Understanding Microgrid Energy Management Systems

A well-functioning microgrid energy management system requires effective operational planning, enabling it to issue control commands to various components, monitor their execution, and make adjustments as necessary. Achieving these functionalities necessitates a robust capability for data collection and information transmission, thereby setting requirements for terminal devices.

In traditional power information transmission, the communication between the main station and terminal devices encompasses four key aspects, commonly referred to as the “Four Remotes” – “remote signaling,” “remote measurement,” “remote control,” and “remote adjustment.” The main station collects real-time status information and electrical data from terminal devices, issuing remote control and adjustment commands based on embedded logic while continuing to gather relevant data to assess the outcomes of these adjustments.

As the current power system has integrated numerous distributed energy resources (DERs) and commercial energy storage devices that belong to users, the impact of these generation and consumption facilities on grid operations has become increasingly unpredictable and partially uncontrollable. Consequently, with the rising penetration of such resources, national guidelines mandate that distributed energy sources must possess the “Four Observable” capabilities: “observable,” “measurable,” “adjustable,” and “controllable.”

The “Management Measures for the Development and Construction of Distributed Photovoltaic Power Generation” Q&A (2025 Edition) provides specific definitions for the “Four Observables”:
– Observable: The operational status of distributed photovoltaic projects can be monitored in real-time, including key data on equipment performance, environmental parameters, and power output.
– Measurable: Distributed photovoltaic projects must have the capability to accurately measure generation power, voltage, and current.
– Adjustable: Distributed photovoltaic projects can adjust active/reactive power output according to grid load demands.
– Controllable: Distributed photovoltaic projects can be remotely or automatically controlled by the grid.

I feel that this explanation could be more detailed, as there is some overlap in the definitions of observable and measurable. For instance, key data on power output should inherently include measurements of generation power, voltage, and current. Hence, setting aside this explanation, let us compare the traditional “Four Remotes” with the contemporary “Four Observables,” drawing on some interchangeable concepts.

Starting with Remote Signaling, this involves data collection. When data flows from the main station to terminal devices, it is termed downlink, while the reverse is called uplink. Remote signaling refers to the request made by the main station for the operational status of terminal devices, which must be convertible to binary form (0-1). This means that the main station determines the current operational status of terminal devices, such as whether they are running or stopped, based on received data classified as either 0 or 1. For example, the operational status of a switch can also be represented in binary. Additionally, terminal devices are preconfigured to recognize potential fault types; if a fault occurs, the corresponding indicator changes to 1; otherwise, it remains 0. When the main station receives these fault status bytes, it can interpret whether a specific fault exists according to the communication protocol.

Next is Remote Measurement, which, like remote signaling, involves data quantity but focuses on specific numerical values rather than states. For instance, this includes the current voltage of a bus or the current flowing through device A. The electrical data provided by terminal devices can be categorized into two types:
1. Raw data collected, such as current and voltage from current and voltage transformers, and environmental temperature and humidity data.
2. Derived electrical data calculated from raw data, such as power values, energy amounts, and power factors, which are computed directly within terminal devices.

When the main station inquires or when terminal devices proactively send data at specific intervals, this timestamped data can be recognized and stored in the main station’s registers, preserving it as historical data for future reference. Unlike remote signaling, which transmits state values, remote measurement delivers actual numerical data.

Moving to Remote Control, this entails issuing commands from the main station to terminal devices based on current remote signaling and measurement data. The remote control commands primarily enable specific control items previously agreed upon between the terminal and the main station. For instance, controlling a switch directly manipulates its state to either 0 or 1. There are also enabling commands, such as setting the power factor for a photovoltaic inverter, which requires first enabling the feature before specific data commands can be issued.

Remote Adjustment follows remote control, allowing the main station to set specific control parameters once a control function is activated. For example, the bidirectional power converter’s charging/discharging power value in an energy storage system or the power factor setting for a photovoltaic inverter can be adjusted. In essence, remote control and remote adjustment may be viewed as opposite operations to remote signaling and measurement.

In comparing the “Four Remotes” and “Four Observables,” the concepts align closely, and an additional forecast element can be integrated into the new energy terminals. My understanding of these concepts is as follows:
– Observable corresponds to remote signaling, enabling the perception of various operational states of a distributed energy source. In a microgrid project involving sources, networks, loads, and storage, key devices such as inverters, meters, and critical switches must be online and able to provide operational status on demand. While the main station cannot visually observe the devices, it can ascertain their statuses through binary indicators.
– Measurable ties to remote measurement, emphasizing actual operational data while incorporating predictive capabilities, such as forecasting generation output or load consumption for specific user points, which is crucial for distributed energy resources participating in electricity markets to optimize profitability.

The concepts of controllable and adjustable align with those of remote control and adjustment, which I will not elaborate on further. As distributed energy sources, controllable and adjustable terminals primarily refer to inverters, which can be started or stopped and adjusted for active load reduction or power factor. The adjustable parameters include the inverter’s output power setting, normally at 100% of its rated capacity. If set to 50%, a 100 kW inverter, regardless of optimal sunlight, can only output 50 kW. The adjustable power factor allows for changes in the active and reactive output of the inverter, with a default unit power factor of 1, indicating only active output.

Once terminal devices possess these functionalities, they establish a foundational data layer. In reality, the intelligent part of a control system resides within the main station, with terminal devices acting as various extensions that can promptly sense conditions and execute commands.