With the deep development of the world economy and the acceleration of the process of international industrialization, the demand for energy in the world is growing, the rate of energy consumption continues to grow, and conventional energy resources are already facing depletion. In order to alleviate the energy crisis, governments and researchers around the world have carried out research on the development and utilization of renewable energy. Known as "blue sky and white coal"
As an inexhaustible, clean and pollution-free renewable energy source with large-scale development and utilization prospects, wind energy has received universal attention. The main form of wind energy utilization is wind power generation. From a global perspective, grid-connected power generation of large and medium-sized wind turbines has become the main form of wind energy utilization. In order to reduce production costs and improve the economic benefits of wind power generation, countries around the world continue to raise the stand-alone capacity of wind turbines. The wind turbines that are currently on the market in foreign countries are mainly 500kW. China's wind energy resources are very rich, and the wind energy that can be developed and utilized in China. The total amount of resources is about 253 million kilowatts. However, in terms of utilization and development of Fengneng, there is a big gap with the world's advanced level. The independent production capacity of large-scale grid-connected wind turbines is relatively poor, mainly relying on foreign imports. The control system of wind turbines is also designed and manufactured by foreign countries. The cost is higher. During the “Ninth Five-Year Plan†period, we undertook the research and development of the electrical control system for 600kW large-scale wind turbines. For the stalled grid-connected wind turbines, the wind turbine control system and device developed by ourselves have been invested in the Xinjiang Dabancheng Wind Farm. Run and run well.
In the process of development, we fully consider that wind turbines operate in a more vicious and unattended condition of the natural environment, and have high requirements for reliability and safety of control. Because programmable logic controller (PLC) is widely used in industrial control field, it has high reliability and strong anti-interference ability, which is very suitable for working in harsh environments. Combined with the control requirements and actual characteristics of wind turbines, we selected Siemens S7-300 programmable controller (PLC) as the central controller.
2 System composition and function The wind turbine control system is the core of the normal operation of the unit. Its control technology is one of the key technologies of the wind turbine. It is closely related to other parts of the wind turbine. Its precise control and perfect function will directly affect it. Safety and efficiency of the unit. Therefore, the control system is the "brain" of wind turbine operation, which is a reliable guarantee for the normal and reliable operation of the entire unit and for optimal operation. The components of the control system mainly include: the main circuit, the control circuit, the sensor and its communication interface.
2.1 System Composition The main circuit is the main power distribution system of the wind turbine. It mainly completes the generator and power grid (including reactive power compensation device, soft grid-connected control device), various actuators (such as motors, solenoid valves, etc.) and control loops. Connection. When the central controller PLC issues a control command, the main circuit connects the generators and the actuators in the fan to a strong electric control circuit and provides power, and the power supply level is high (such as AC 690V, 400V, 220V, 24V, DC 24V). At the same time, feedback signals (such as contactor pull-in, circuit breaker tripping and other feedback signals) are sent to the central control PLC for condition monitoring of actuators such as contactors, motors, and power supplies.
The control circuit is composed of a PLC central controller and its function expansion modules. It mainly realizes the normal operation control of wind turbines, the safety protection of various parts of the unit, fault detection and processing, modification of operating parameters, data record display and manual operation, and the configured communication interface realizes local communication and remote communication.
Sensors and communication interface sensors mainly include anemometers, wind vanes, vibration acceleration sensors, rotational speed sensors, temperature sensors, yaw position sensors, pressure switches, and cable switches, etc., for collecting and monitoring various types of wind turbines in operation. Operating parameters, including wind direction, wind speed, hydraulic system pressure, tip pressure, hydraulic oil level, gear oil pressure, gear oil level and gear oil temperature, brake wear, unit vibration, new cable, generator and its bearing temperature, and generator And parameters such as impeller speed.
Control system structure diagram Communication interface includes CP communication processor (RS485), CPU configured MPI and PR0FIBUS communication interface. The CP communication processor (RS485) communicates with the power collection module to collect grid parameters; the MPI communication interface configured by the CPU communicates with the operator panel, and displays the operating status and operating parameters of the unit through its liquid crystal display, and realizes each through its keyboard operation. Kind of control function; PR0FIBUS communication interface is remote communication with PC in central control room, real-time monitoring of wind turbine operation status, operation data, accumulated data storage, recording fault conditions, manual yaw, reset, start, stop, etc. operating. The control system structure is shown in the figure.
2.2 System function The control system not only needs to realize the normal operation control of the wind turbine (such as automatic start, stop, etc.), but also monitors the operation status of the wind turbine (such as grid parameters, temperature, etc.) through the communication interface, and also needs to have safety protection functions. Therefore, the control system mainly realizes three functions of normal operation control, parameter monitoring and monitoring, and safety protection and processing.
The normal operation control includes wind turbine automatic starting soft grid connection, large/small generator automatic switching, generator dehumidification heating, unit automatic wind setting, hydraulic system automatic opening and closing, gear oil pump automatic start and stop, gear oil heater, cooling Start and stop, cabin twisted cable and automatic cable unwinding, capacitor compensation automatic group switching and negative power automatic shutdown.
Parameter monitoring and monitoring includes three-phase voltage, frequency, generator output, input current (two-way monitoring), active power (two-way monitoring), reactive power, power factor, wind speed, wind direction, impeller speed, generator speed, hydraulic pressure System condition, yaw system condition, soft grid connection and other working conditions, gear oil temperature, large/small generator winding temperature, generator front/rear bearing temperature, control cabinet temperature, cabin temperature, ambient temperature. The controller makes a judgment based on the signal provided by the sensor to control the reliable and safe operation of the fan. Realize human-computer interaction with the local operator panel, query the wind turbine operating status, display the fault status, set the operating parameters and control operations: manual start/stop, reset, manual yaw; at the same time, the controller configures the interface for remote monitoring communication. Monitor operating conditions and fault conditions, collect fan operating data, and control commands issued to the turbine.
The security protection and processing system is divided into three layers: computer system, security chain protection independent of the computer, and protection measures of the device itself. The protection measures of the device itself mainly adopt hardware protection measures according to the characteristics of the device itself, such as adding RC absorption circuit at both ends of the coil; the computer system detects the faults occurring during the operation of the wind turbine, and separately performs alarm according to the type of fault. Normal shutdown, safe shutdown and emergency shutdown, etc., at the same time, for self-reset faults and non-self-reset faults/re-automatic start or manual start of wind turbines, to achieve the dual functions of protecting the safety of the unit and improving the availability of the unit; independent of The computer's safety chain is a hardware protection circuit designed when the unit has an abnormal fault or a computer system out of control.
3 hardware design S7-300 is a modular small PLC system, but can meet the requirements of medium performance, mainly has the following characteristics: a wide range of functional modules can meet and adapt to automatic control tasks; simple and practical decentralized structure and multiple interfaces Network capability; flexible control, reliable, user-friendly; module expansion is convenient and flexible when control tasks increase; wind turbine control signals mainly have switching input signals, switching output signals, analog input signals (such as temperature) , frequency signals (such as speed, wind speed). According to the control requirements of wind turbines and the characteristics of the signals to be controlled, and making full use of the resources of S7-300, the S7-300 programmable controller is configured as follows: power supply; CPU315-2DP, 64KB working memory, load memory integrated 96KBRAM, maximum It can be extended by 512KB, the MPI interface can communicate with the 0P7/DP operation panel; the PROFIBUSDP interface can communicate with the remote central control room PC; the FM350-2 intelligent counting module, 8 channels, for general counting and measurement tasks, can be directly It is connected with 24V incremental encoder and NAMUR encoder to realize frequency measurement, speed measurement, cycle measurement, and has comparison function and interrupt processing function for fault; CP communication processor module, RS485 interface, can realize PPI communication. Communicate with the power transmitter to realize the detection of grid parameters (including three-phase voltage, three-phase current, active programmable controller application notebook6 power, reactive power, frequency, power factor, etc.); 0P7/DP keyboard display and Operation panel, LCD display 4 rows and 20 columns, one RS232 communication interface, can be connected with PLC/computer/printer; one RS485 interface, can be connected with PLC or computer, 128K bytes, 8 function keys (F1-F4, K1 ~K4) can be configured to perform different control functions.
The program is compiled in a modular structure, including main program, event processing subroutine, hardware interrupt program, and timer interrupt program.
The main program mainly controls the normal operation and safety protection of the wind turbine, including sub-programs such as calling wind turbine automatic or manual start soft grid control, shutdown, large/small motor switching control, reactive power compensation capacitor investment. Its block diagram is as shown.
4.2 event processing subroutine bookmark9 check system pressure pressure communication processing subroutine parameter initialization communication connection grid parameter ft detection safety stop subroutine emergency stop subroutine automatic start network subroutine manual start network subroutine automatic yaw subroutine clockwise Solving cable program counterclockwise solution cable program side wind 90 degree subroutine gear oil pump control subroutine hydraulic oil pump control subroutine gear oil heating subroutine gear oil cooling subroutine generator heating subroutine reactive power compensation subroutine 4.3 hardware interrupt program The digital input template with interrupt capability is selected. When the hardware detects the change of the field signal (when the fault occurs), the hardware interrupt processing block OB40 is executed. According to the fault level, normal shutdown, safe shutdown or emergency is performed in OB40. Stop the machine to ensure timely processing of the fault.
Since the temperature signal is a slow-changing signal, the temperature value can be collected periodically, and temperature control and monitoring can be realized in the timer interrupt program.
In order to ensure the safe and reliable operation of the wind turbine, the safety protection link adopts the hardware protection measures while using the software protection. When the unit has abnormal faults or the control system fails, the wind turbine is kept in a safe state.
5.1 Software Security 1. Fault Tolerance Design In order to prevent the user from malfunctioning due to misoperation, the illegal keyboard and button input are not recognized in any state of the wind turbine.
2. Software authority design The wind turbine control software has three levels of authority: (1) The lowest user layer authority is used by the wind farm duty personnel, allowing the status display of the wind turbine generator group, fault display, fault record, running cumulative value, etc. Controlled wind turbines start and stop and yaw left and right.
(2) The maintenance layer authority of the first level is used by maintenance personnel, and a password is required. In addition to the user layer's authority, it can also be turned down (page 73) to indicate the specific indication signal of the accident trip, and can be manually or automatically reset.
2.1 Central accident double number device realized by PLC. 2 Ladder diagram and command 2.3 PLC central accident signal device works as shown in the figure, the central accident signal device is composed of FX2-16 PLC. When any loop trips, because the SA control switch in the loop and the auxiliary contact of the breaker press the "non-corresponding principle", X0 is input with a signal. According to the program programmed in the PLC, Y0 has output and electricity. The whistle is called, and it will automatically reset after 10 seconds, waiting for the next meal.
When another circuit trips again, there is another signal input X0, which is also triggered by the rising edge circuit, so that Y0 has input again and alarms.
In the device, the XI terminal is connected to a normally closed button SB2 for use as a manual reset alarm device.
The SB1 acts as a test button.
2.4 PLC Central Accident Signal Device Features As can be seen from the above, the central accident signal device realized by PLC has few external wiring and equipment, so the wiring is very simple; the program control replaces the relay control, so the reliability is very awkward, and the change is very flexible. Convenient; saves a lot of relays, consumes very little power; 3 Conclusion Through the comparison of the above two methods, we obviously found that PLC control is far superior to relay control. As technology continues to advance, PLC control will increasingly be used in all aspects of production and practice.
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