Overview
With the continuous increase in installed wind power capacity in recent years, the proportion of wind power in the power grid has also been steadily increasing. As is well known, wind energy is highly volatile and intermittent, so large-scale wind power integration poses numerous serious challenges to power supply and demand balance, power system security, and power quality. The multiple grid disconnection incidents that occurred in Jiuquan, Gansu, and other areas in early 2011 also illustrate the urgency of formulating wind power grid connection standards. Therefore, the State Grid Corporation of China has proposed technical regulations for wind farm grid connection, leading to the concepts of grid-friendly wind turbines and wind farms.
1. The wind turbine has active and reactive power regulation and low voltage ride-through capability to ensure that the wind turbine is not disconnected when the power grid fluctuates;
2. The wind farm has a wind power prediction system that can complete short-term power prediction within 48 hours and ultra-short-term power prediction from 15 minutes to 4 hours.
3. Centrally optimize the configuration of active and reactive power control systems to achieve remote adjustment and control of the wind turbines.
Based on the above points, many wind turbine manufacturers have proposed the concept of intelligent wind farms. These farms utilize a network to remotely and centrally monitor the operation of wind turbines and the entire wind farm, enabling real-time power control. This requires high-performance turbine controllers, corresponding power measurement equipment, and fast fieldbuses. Beckhoff Automation GmbH, a German company, offers PC-based control technology with excellent openness and flexibility. Beckhoff's product line includes industrial PCs, I/O, fieldbus components, and TwinCAT automation software. High-performance PCs and fully functional terminal modules provide comprehensive and high-quality power monitoring solutions for wind turbines and wind farms to a wide range of wind power customers.
Real-time power monitoring network for wind farms:
This solution is a real-time network scheme for the dispatch of wind turbine generators and wind farms based on Beckhoff's series of products, as shown in Figure 1 below.
Figure 1 Real-time network for power monitoring of wind farms
This solution is based on Beckhoff's industrial PCs, power measurement terminal modules, EtherCAT couplers with fiber optic interfaces, and real-time EtherCAT technology. The Beckhoff industrial PCs run a dedicated energy management platform with powerful wind farm power monitoring capabilities. This platform provides an interface with the power grid dispatch system, enabling centralized real-time control of the wind farm's voltage, power, and other parameters. This ensures coordinated operation between the wind farm and the grid in the connected area, achieving efficient wind farm operation and management. The EtherCAT optocoupler module connects the energy management platform to the wind turbines within the wind farm, forming a real-time wind farm power monitoring network capable of real-time control tasks within the wind farm network with a response time of less than 1ms. The dedicated power measurement terminal modules, in conjunction with a unique low-voltage ride-through control module, monitor the grid conditions (voltage, frequency, active power, reactive power, etc.) at the wind farm's common grid connection point and on the grid-connected side of each individual wind turbine.
The real-time network solution for wind farm power monitoring consists of two parts:
1. Power monitoring of a single wind turbine generator set, as shown in Figure 2.
Figure 2 Power monitoring of a single wind turbine generator set
This solution uses Beckhoff's embedded industrial PCCX5020 controller as the main controller for a single wind turbine. The main control program is based on TwinCAT software and utilizes Beckhoff's self-developed, comprehensive, efficient, and mature wind power-specific function library, integrating advanced control algorithms to effectively coordinate and control the operation of various components and subsystems of the wind turbine. Based on current wind conditions and control commands from the wind farm's energy management platform, it controls the wind turbine's output voltage, frequency, and power, ensuring stable operation.
The controller's built-in Ethernet interface can connect to the EL6601 switch module, enabling data exchange with the wind farm's SCADA system via communication protocols such as ADS, OPC, and ModbusTCP. It connects to the wind farm's real-time control network through the EL6692 EtherCAT bridge module and the EK1110 expansion module, communicating with the energy management platform to meet the real-time control needs of the entire wind farm. The EK1501 serves as the access point for a single wind turbine to the wind farm's EtherCAT real-time network.
The EL3413 module can directly monitor the 690VAC voltage, current, frequency, active power, reactive power, power generation, and harmonics up to the 21st order on the grid-connected side of a single wind turbine. The wind turbine main control system monitors the wind turbine's operating status through the collected power data, and the relevant data can be transmitted to the energy management platform and SCADA system in the wind farm's central control room via the wind farm network.
2. Power monitoring at the public access point of the wind farm, as shown in Figure 3.
Figure 3 Power monitoring at the public access point of the wind farm
The EL3773 power measurement module, equipped with XFC oversampling technology, monitors the common access point of the wind farm grid. The energy management platform running on a Beckhoff industrial PC connects to the wind farm's real-time network via an EtherCAT coupler, collecting grid data at the common access point and on the grid-connected side of each wind turbine. A dedicated control program within the platform centrally regulates the voltage, frequency, active power output, and reactive power of the entire wind farm.
Communication architecture:
The wind farm's real-time network is a ring network, using single-mode fiber optic cable to connect the wind turbines in the wind farm into a communication ring network via an EtherCAT bus and corresponding couplers (EK1501). The main controller (CX5020) of each wind turbine in the wind farm can connect to the wind farm network via an Ethernet switch module (EL6601) and uses an EtherCAT bridge module (EL6692) to achieve real-time communication with the energy management platform.
EtherCAT, an open real-time Ethernet communication protocol, is a high-speed Ethernet fieldbus developed by Beckhoff Automation GmbH, Germany. EtherCAT sets a new standard for real-time system performance and topology flexibility, with a refresh time of only 30µs for 1000 switch inputs distributed across 100 nodes. It also significantly reduces fieldbus costs. Other features of EtherCAT include distributed clocking, optional cable redundancy, and a functional safety protocol (SIL3). With XFC (Extreme Speed Control) technology, a time resolution of less than 100ns can be achieved using timestamps.
Key equipment:
CX5020
The CX50x0 series is a fanless, wide-temperature-range embedded controller compliant with standard DIN rail mounting. The CX50x0 utilizes an Intel Atom low-power processor with a CPU frequency of up to 1.6GHz. It features two independent Gigabit Ethernet ports and four USB 2.0 interfaces, and can be connected to Beckhoff control panels or standard DVI displays via a DVI interface. A serial port (RS232/RS422/RS485) or a fieldbus interface with master or slave functionality can be added as needed. Interchangeable CF cards, located behind a cover and removable externally, serve as boot and storage media. The CX5000 series also incorporates a built-in 1-second UPS to ensure safe backup of persistent application data on the CF card.
EK1501/EK1521
EhterCAT couplers and interface modules with fiber optic interfaces; featuring EtherCAT photoelectric conversion and coupling functions. Using couplers and interface modules with single-mode fiber optic interfaces, EhterCAT fiber optic cable redundancy systems can be implemented over distances up to 20 kilometers.
EL3413
Designed specifically for wind power, this module is used for power monitoring of a single wind turbine and can be directly connected to 690VAC without requiring a voltage transformer. The current signal detection channels are isolated and can be connected to various common current transformers. This power measurement module can monitor voltage, current, frequency, active power, reactive power, power factor, power generation, and even the 21st harmonic, among other related indicators.
EL3773
The EL3773 oversampling power measurement module employs Beckhoff XFC technology, enabling simultaneous sampling of six channels with an accuracy of 100µs. Based on the sampled current and voltage, customers can calculate the true RMS value and implement complex custom algorithms. Distributed clocking is supported.
EL6692/EL6601
The EL6692 is used for data exchange between EtherCAT network segments of different master stations, and it can also synchronize the distributed clocks of each network segment.
The EL6601 is an Ethernet switch module used to distribute Ethernet devices to an EtherCAT terminal block network. The switch terminal block can be installed anywhere in the EtherCAT network segment without any configuration.
Beckhoff's wind power function library greatly facilitates the development of wind turbine main control systems.
Drawing on Beckhoff's years of experience in developing wind power main control systems, this is a highly efficient and mature wind power function library. The Beckhoff wind power function library is modular in structure and its source code is completely open, helping engineers gain a deep understanding of wind turbine control. Using these function libraries can significantly shorten the development time of the main control program and can also optimize the main control architecture, control code, and logic of existing programs. Its main software modules include:
1. Library: Wind Auxiliaries (Wind Power Auxiliary Library)
2. LibraryStatuscodes/StatuscodeGenerator (Status code library and generation tool)
3. TraceLogger (status log file)
4Mean-ValueLogger (Mean Record)
5. PowerCurveLogger (Power Curve Recording)
6Simulation (Wind Turbine Simulation Library)
7. I/O Generator (I/O generation tool)
8. ParameterGenerator (parameter generation tool)
9. RemoteCommandGenerator (Remote Command Generation Tool)
Beckhoff TwinCAT3 software
Beckhoff established a global standard for PC-based automation technology as early as 1986. In terms of software, TwinCAT (The Windows Control and Automation Technology) is used as the core software for its control systems. TwinCAT software transforms any PC-based system into a real-time control system for multiple PLCs, NCs, CNCs, or robots. TwinCAT3 is the result of Beckhoff's more in-depth and systematic research and development based on TwinCAT2 software. The following lists some features of TwinCAT3, and Figure 4 shows a TwinCAT3 system diagram:
Programming and configuration only require one software
Integrating Visual Studio
More flexibility in choosing a programming language
Supports object-oriented IEC61131-3
Using C/C++ as the real-time application programming tool
Supports Matlab/Simulink
Supports multi-core and 64-bit systems
The TwinCAT2 solution can be directly ported to TwinCAT3.
Company Profile:
Beckhoff Automation GmbH is headquartered in Welsh, Germany. With branches worldwide and global partners, the company currently operates in over 60 countries.
Beckhoff has always adhered to the development philosophy of PC-based automation technology. Its industrial computers, fieldbus modules, drive products, and TwinCAT control software constitute a complete and compatible control system, providing open automation systems and complete solutions for various industrial control fields. For nearly 30 years, Beckhoff's components and system solutions have been widely used around the world.
Since Beckhoff established its Beijing representative office in March 2001, the company's business in China has developed rapidly. Representative offices were subsequently established in Shanghai and Guangzhou, with liaison offices in Ningbo, Wuhan, Chengdu, and Qingdao. In August 2007, the Shanghai representative office underwent restructuring and officially became Beckhoff China, relocating the company's China headquarters to Shanghai. With the continuous introduction of various new products and technologies offering excellent cost-performance into the Chinese market, Beckhoff's commitment to breaking traditional control models and promoting new PC control technologies has been increasingly accepted by Chinese users.
Contact information:
www.beckhoff.com
www.beckhoff.com.cn
