F. Alejandro Vaquer Puigcerver
Raúl Sebastiá Forcada
NI Products Used:
LabVIEW 2017 SP1
LabVIEW 2017 Real-Time Module
NI Industrial Driver IEC 60870-5-104 for Real-Time
The mandatory international compliance of Grid Codes (GC) in Intermittent Renewable Resources (IIR), like Photovoltaic Generation (PV) facilities has become a critical technical point where it is necessary to have efficient, reliable, flexible and adaptable solutions, not only to accomplish with the regulation but also to provide an economic improvement to these facilities.
This Power Plant Controller (PPC) is based on our i-less monitoring and control framework which is entirely built on the LabVIEW platform. Our framework has allowed us to develop the different communication protocols, the necessary control loops, as well as their easy integration with third parties. Furthermore, taking advantage of the reliability of the cRIO platform, we have been able to deal with the intercommunication with the electric power company, by providing an IEC 60870-5-104 hot-hot mode redundant gateway built with two units of cRIO-9064 and LabVIEW Real-Time.
Nowadays, the IIR installations are subject to the fulfillment of the distribution network GC. Additionally, there are a large number of commercial brands of photovoltaic inverters, energy measurement and field devices in the market, and several electrical grid topologies in the design of the Points of Injection (POI) in the PV plants. Therefore it is necessary to have solutions that are sufficiently powerful, flexible and reliable to be able to run the regulation control tasks and the exchange of signals with the signed control central through an industrial network protocol, as well as by the necessary flexibility to improve the economic efficiency of the plants.
Mainly, the control must deal with following modes:
The ability of our PPC to adapt dynamically the operation to the current feeding topology is a greater added value to the ACWA POWER company, because it reduces the lack of plant production. Through a control algorithm, implemented in the PPC itself and based on the real-time information of the local meteorological stations and the information of the network analyzers located in the Point of Injection (POI), we can optimize the production and maximize the active power exported within the limitations imposed at any time by NEPCO, for instance in case of cloudy weather by balancing the production between the two feeders.
We receive the control parameters directly from the electrical substation through the IEC 60870-5-104 protocol, and the system also publish specific information about the state of the PV energy plant, through two redundant gateways operating as IEC-60870-5-104 controlled stations and Modbus TCP masters to transfer the information to the PPC controller.
At the PV side, we integrated two network analyzers located at the POI, nine meteorological stations, nine protection relays, twenty-four tracker Network Control Units (NCU) and twenty-four Power Electronics inverter brand. All inverters are individually controlled because the PPC implements an advanced state machine algorithm. The Ethernet communication network is made through a fiber ring physical layer, and the field protocols are Modbus TCP and Modbus RTU.
The controller has two independent 1s Proportional Integrated Derivative (PID) control loops, 250ms field devices reading loops and its own monitoring and datalogging system with more than 1,000 variables / alarms monitored at 1 second scan rate, to be able to analyze afterwards the historical data. There are two developed interfaces, one is a Windows desktop service application developed with LabVIEW for both configuration and fast monitoring and diagnostic tasks, and the other is a thin client Web Application made in HTML5 and supported by LabVIEW RESTful web services, to monitor at low speed and to perform high performance queries to the historical databases through a web browser. For its integration with a third party system, the PPC controller publishes all the information through Modbus TCP and OPC-UA protocols.
The system is supported by an industrial-grade miniPC with an Intel Atom Quad Core E3845 1.91GHz, 4GB RAM and 64GB SSD. On the other hand, the redundant gateway is integrated by two cRIO-9064 units, interconnected by means a RS232 serial bus to perform the hot-hot mode redundancy.
The flexibility, speed and performance of both LabVIEW and the cRIO technologies have allowed us to deal with this kind of high demanding and precise solutions and reaching a high reliability product. The benefits to our customers are a low cost product even the high degree of customization and a fast way to setup the system on site.
Author Contact Details:
Avda. La Murà, 3 Entresuelo
Tel.: +34 964 515210