High Level Architecture

This section presents an overview of the architecture of the RAS. The architecture primarily consists of (a) Data sensors (b) Data Aggregator (c) Substation Local Area network (LAN) (d) Wide Area Network (WAN) (e) Computing nodes (f) Actuators. The architecture is shown in Fig. \ref{fig:Setup}. Following subsections describe these components in brief.

Data Sensors

The proposed RAS uses local and remote measurements of voltage and current phasors measured at each substation. The temperature and wind speed are also required for the proposed RAS. The topology processing is carried out based on the breaker status. The primary source of voltage and current phasors are field sensors like Phasor Measurement Units (PMUs), Digital Fault Recorders (DFR) and Remote Terminal Units (RTU). The PMUs and DFRs transmit phasor data in a periodic fashion at the rate of 1 phasor per second. The RTUs transmit the voltage magnitude and power flow measurements at the rate of 1 set of measurements per second. The weather measurements are periodically updated every 10 minutes. The data form the PMUs and DFRs are time stamped using Global Positioning System (GPS) at the source while the measurements from the RTUs are time stamped by the data acquisition module. The physical interface for data inputs from PMUs, DFRs, RTU, and weather measurements are Ethernet ports. The protocol for input data for PMU and DFR measurements is C37.118 over TCP layer and that of RTUs and weather sensors is DNP3.

Data Aggregator

The measured phasor data, RTU data and weather sensor data is sent to the data aggregator through a substation LAN. This module consists of a Phasor Data Concentrator (PDC). It time aligns the data and the processed data is sent to computing nodes for determining the control actions through a WAN.

Substation LAN

Each substation has a local area network. Sensor data, measured at a substation is sent to the data aggregator in a substation through the substation LAN. The control commands are sent back to the windfarms through the LAN. Various sensors and actuators (relays, etc) are connected to this network.

Wide Area Network

Data from all the substations are communicated to the computing nodes through the wide area network. The control signals, computed is also sent to the respective substations through this network.

Computing Nodes

In the proposed architecture, the computing nodes receive data from all the substations. The data aggregator module time aligns all the data received. The Dynamic Line rating (DLR) module, computes the transmission line capacities based on the weather data obtained through the weather sensors. the RAS module computes the control action (wind power curtailment, in this work) based on the line capacities estimated and the voltage and current phasors.
It is to be noted that there is a backup computing node, having all these modules. It also receives all the phasor data and the weather data simultaneously with the main node. The backup node takes the control actions, only when the main node fails or crashes. Such failures are detected by the backup node using the ”Heartbeat” liveliness module. If any crash is detected, the backup node takes over and computes the control actions, thus providing the resiliency.

Actuators

The actuators receive the control commands (curtailment commands) from the computing nodes through the wide area network and issue these commands to the wind farm controls through the substation LAN.