Power collection system for large wind turbines
As a rich and clean green energy source, wind energy is the most renewable energy source with large-scale development and utilization prospects in the near future. Networked power generation for large and medium-sized wind turbines is currently the main form of wind energy utilization worldwide. China's wind energy resources ranks among the top in the world, but China's wind energy development and utilization level lags far behind the international advanced level, and the wind turbine's independent production capacity is poor. During the "Ninth Five-Year Plan" period, the Institute of Electrical Engineering of the Chinese Academy of Sciences conducted a scientific and technological research on the electrical control technology of the 600/125kW fixed-pitch stalled double-winding wind turbine. The electrical control system of the unit is based on the Siemens S7-300 programmable controller. (PLC) control. At present, the task of tackling the key has been successfully completed. The developed electrical control system has been in operation with the whole machine in the Dabancheng Wind Farm in Xinjiang, and the situation is good. Among them, the collection of electricity parameters is an important part of the electrical control system. In the electric control system of the wind turbine, the PLC needs to collect the three-phase voltage, current, power factor, frequency, power and power generation parameters of the power grid at any time and track the changes of the grid parameters in time to ensure that the wind turbine can operate normally safely and reliably. . In addition, the power parameter is also an important basis for data statistics of the electronic control system.
2 Wind Turbine Power Acquisition System Design 2.1 Selection of Communication Module If the signal interface circuit composed of discrete components is used to process the voltage and current parameters, it not only reduces the reliability and anti-interference of the system, but also occupies the PLC. Many I/O resources. Considering that the electric control system of wind turbines works in the harsh natural environment and strong electromagnetic interference, it puts high requirements on the reliability and anti-interference of the control system. For this reason, we chose the WBZ isolation of Southwest Automation Research Institute. The multi-parameter power acquisition module and the "30 CP340 module" with communication function of the Siemens S7300 series PLC. The WBZ module has a data communication function, which can transfer each grid parameter to the CP340 according to the set communication protocol, and then the CP340 transmits the data to the data storage area of ​​the PLC through the bus on the back of the module.
2.2WBZ electric collection module communication protocol design WBZ type power collection module is powerful, high measurement accuracy, strong anti-interference, can carry out three-phase active power (E), three-phase reactive power (only), three-phase Active power (P), three-phase reactive power (Q), power factor (C), frequency (/), three-phase voltage (t / a, L / b, and three-phase current (a, 4, a total of 12 The measurement of the power grid parameters, the accuracy level and range of the measurement are respectively less than 300ms. The CP340 module integrates three asynchronous serial communication standards and adopts the RS485 communication interface suitable for half-duplex communication. The CP340 module is for different communication. The interface is preset with three serial communication interface drive protocols: PRINTER protocol, ASC protocol and 3964(R) protocol. The PRINTER protocol is only used for one-way data communication, and the 3964(R) protocol is only used for half-duplex communication. ASC protocol is a data transmission protocol that can be used for point-to-point connection between communication bodies. It is applicable to RS232C, RS422/485 and 20mA current loop three asynchronous serial communication interfaces, which can be used for full-duplex communication of half-duplex communication. And 3964 (R The protocol does not apply to the RS485 serial communication interface; when the RS422/485 serial communication interface is selected, the ASC protocol is applicable to both the RS485 communication interface of the two-wire connection method and the RS422 communication interface of the four-wire connection method. Here, the ASC protocol is selected, and the level between the two data lines is set to R(A): 0V, R(B): 5V. Under the RS485 communication interface and the ASC protocol, the CP340 module has three kinds of work for judging whether the received data frame is finished or not. Mode: 1 byte delay time cutoff. 2 Receive end code cutoff. 3 Receive a fixed number of bytes cutoff. Byte delay time cutoff means that when the CP340 receives data, when the last byte of the data frame arrives, When the delay time expires, it indicates that the frame data reception is finished. In this way, the byte delay time needs to be defined. When the end code is received, when receiving the data, if a defined end code is received, the data is stopped. In this case, the end code needs to be defined, and it must be consistent with the end code sent by the slave. If the same data as the end code appears in the transmitted data frame, the data needs to be disconnected and sent.
The third way is to stop receiving after receiving a certain number of data bytes. This method is suitable when the number of response frame bytes sent by the slave is fixed. The second way of working is used here.
2.4 Implementation of the most electric acquisition system According to the set communication protocol, the CP340 module (master station) first issues a command frame to the power collection module (slave), and the power collection module responds after receiving the command frame, and sends a response frame, each The response frame has a length of 30 bits. This response frame contains the grid parameters we want. The order of the output data is set as follows: three-phase active power (E), three-phase reactive power (R), three-phase active power. (P), three-phase reactive power (Q), power factor (C), frequency (/), three-phase voltage 7a, Ub, U and three-phase current (18, 4, the primary station receives each response frame An interrupt is generated after the byte, and it is judged in the interrupt program whether the byte is the defined data frame end code, which means that the frame data is received, and if not, the reception continues. The primary station sets after receiving each data frame. The program is interrupted and a command frame is then sent to the slave in the interrupt routine.
Since the power detected by the power collection module is mostly real-time data, if a communication error occurs for some reason, such as frame dropping, garbled, etc., the frame is ignored at this time; if the power detected by the power collection module is an important parameter that cannot be lost, such as electricity Degree (incremental), reliable transmission of data must be ensured to avoid cumulative errors.
For the first case, the upper computer does not need to confirm; for the second case, the frame number of the current transmission data frame is first fed back to the power collection module, and then the confirmation information of the upper computer is waited for. If the power collection module does not receive the confirmation command, the power collection module retransmits the old data when the host computer issues the read data command again; if the power collection module receives the confirmation command, the old data is cleared. When the host computer issues the read data command again, the power collection module transmits new data.
The structure of the power storage system of the wind turbine is shown in the figure. When the CP340 module communicates, it mainly uses two data communication modules to implement. The data is transmitted using P-SEND, and the received data is P-RCV. The command to send the command frame is as follows: Address of CP340 The power collection system of the large wind turbine receives the response frame as follows: :=13// Indicates the data to be stored. The data block DBfrNO: = 0 / / indicates the starting address in the data storage data block NDR: = M64.0 ERROR: = M64.1LEN: = MW72STATUS: = MW70 grid. The processing segment of the S data communication result is used to store the received response frame information. However, the collected data cannot be directly used and needs to be processed by the data format. The unit of three-phase active power and reactive power is the 10,000-point value of the nominal value, so it needs to be converted into floating-point number first, and then divided by 10000 to obtain floating-point data in units of kW; the unit of power factor is 10,000 of the nominal value. Score, you need to convert the data into floating point number, then divide by 10000; the frequency can be accurate to 0.01Hz, first convert the data into floating point number, then divide by 100, get the floating point data in Hz; the unit of three-phase voltage It is the tens of fraction of the nominal value, so after being converted to a floating point number, dividing by 10000, the floating point data of unit V is obtained; after the three-phase current is converted into a floating point number, according to the coefficient of the selected current transformer, after simple processing Get the floating point data in unit A.
3 Conclusion The power collection system has been put into operation on site as part of the wind turbine electrical control system, and has achieved satisfactory results. More than one year of operation shows that the system is reliable in operation and strong in anti-interference. The electronic control system can accurately and quickly track changes in various parameters of the power grid and respond in time to ensure the wind turbine electrical control system and remote monitoring system. The normal operation.
(Continued from page 22) 3 Chen Degui. Foreign intelligent motor protection relays and controllers. Low pressure 6 Lin Shizhuang, Cai Zexiang. Large motor fault diagnosis is reviewed in the protection theory. Guangdong Electric Power, 2001 (6) 7 Wang Yi. The characteristics and applications of fieldbus technology. Communication power technology,
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