I. System Overview
Wind farms are characterized by a wide range of turbine layouts and harsh natural operating environments. The WPCS wind power control system is specifically designed for large wind turbine units. The product integrates the most advanced power electronics, microelectronics, networking, and software technologies. The system's network structure is as follows:
Wind power control system network structure diagram
The WPCS wind power control system includes on-site wind turbine generator control units, high-speed ring redundant fiber optic Ethernet, and remote host computer operator stations.
II. Wind Turbine Generator Control Unit (WPCU)
The wind turbine control unit (WPCU) is the core of each wind turbine's control system, distributed throughout the tower and nacelle. Due to the harsh operating environment of wind turbines, the reliability requirements for the control system are extremely high. The WPCS wind power control system is specifically designed for the operational needs of large-scale wind farms, featuring excellent environmental adaptability and resistance to electromagnetic interference. Its system structure is as follows:
The field control station of the WPCS wind power control system includes: tower main controller rack, nacelle control station rack, pitch control system, converter system, field touch screen station, Ethernet switch, fieldbus communication network, UPS power supply, emergency shutdown backup system, etc.
III. Remote Monitoring System (WPCM)
All wind turbines are connected to the host computer operator station in the main control room via fiber optic Ethernet, enabling remote monitoring of the entire wind farm. The host computer monitoring software has the following functions:
① The system has a user-friendly control interface.
② The system displays the operating data of each unit, such as the instantaneous power generation, cumulative power generation, power generation hours, wind turbine and motor speed, wind speed, wind direction, etc. The data from the lower-level machine is loaded into the upper-level machine and displayed on the monitor. If necessary, it can also be displayed intuitively in the form of curves or charts.
③ The system displays the operating status of each wind turbine, such as start-up, shutdown, directional adjustment, manual/automatic control, and the operation of large/small generators. By observing the status of each wind turbine, one can understand the overall operation of the wind farm.
④ The system can promptly display faults that occur during the operation of each unit.
⑤ The system enables centralized control of wind turbine units. From the central control room, operators can change settings and control lower-level machines simply by pressing the corresponding keys labeled with a specific function.
⑥ System Management. The monitoring software has the functions of timed printing of operating data, manual real-time printing, and automatic recording of faults, so as to view the historical records of the wind farm's operating status at any time.
IV. Functions of the WPCS Wind Power Control System
The WPCS wind power control system has the following basic functions:
1. Data Acquisition (DAS) Function
The relevant parameters monitored during unit operation include:
(1) Power grid parameters, including three-phase voltage, three-phase current, power grid frequency, power factor, etc. Voltage fault detection: power grid voltage flicker, overvoltage, undervoltage, voltage drop, phase sequence fault, three-phase asymmetry, etc.
(2) Meteorological parameters, including wind speed, wind direction, ambient temperature, etc.
(3) Detection of unit status parameters, including: wind turbine speed, generator speed, generator coil temperature, generator front and rear bearing temperature, gearbox oil temperature, gearbox front and rear bearing temperature, hydraulic system oil temperature, oil pressure, oil level, nacelle vibration, cable torsion, nacelle temperature, etc.
2. Unit start-up and shutdown, power generation control
(1) The main control system detects the grid parameters, meteorological parameters and unit operating parameters. When the conditions are met, the yaw system is started to perform automatic cable release and wind control, release the unit's brake disc, adjust the pitch angle, and the wind turbine begins to rotate freely and enters standby mode.
(2) When the wind speed monitored by the external meteorological system is greater than a certain value, the main control system starts the converter system to start rotor excitation. When the generator stator output power is in the same frequency, phase and amplitude as the power grid, the output circuit breaker is closed to realize grid-connected power generation.
(3) Wind turbine power and speed regulation
Based on the characteristics of wind turbines, the turbine will capture the maximum energy when operating at the optimal tip speed ratio λ. Although theoretically the turbine can operate at any speed, due to actual turbine speed limitations and system power limitations, this stage must be divided into the following operating regions: variable speed operation region, constant speed operation region, and constant power operation region. The operating states within the rated power range include: the variable speed operation region (optimal λ) and the constant speed operation region.
When the wind turbine is connected to the grid, if the speed is lower than the limit speed and the power is lower than the rated power, the speed of the wind turbine is adjusted according to the current actual wind speed so that the unit operates in the state of capturing maximum wind energy.
3. Logic of auxiliary equipment in wind power control system
(1) Generator system
The generator's operating parameters are monitored, and the generator coil temperature, bearing temperature, and slip ring chamber temperature are controlled within appropriate ranges through three cooling fans and four electric heaters. The relevant logic is as follows:
When the generator temperature rises to a certain set value, the cooling fan starts; when the temperature drops to a certain set value, the fan stops running. When the generator temperature is too high or too low and exceeds the limit, an alarm signal is issued and a safety shutdown procedure is executed.
When the temperature drops to a certain set value, the electric heater is started; when the temperature rises to a certain set value, the heater stops operating. At the same time, the electric heater is also used to control the temperature difference of the generator within a reasonable range.
(2) Hydraulic system
The unit's hydraulic system is used for yaw system braking and mechanical brake disc drive. Under normal conditions, the unit must maintain operation within the rated pressure range.
The hydraulic pump controls the pressure of the hydraulic system. When the pressure drops to a set value, the oil pump starts running. When the pressure rises to a certain set value, the pump stops.
(3) Meteorological system
The meteorological system is an intelligent meteorological measuring instrument that communicates with the controller via an RS485 port to collect meteorological parameters from outside the cabin and transmit them to the control system.
The heaters in the meteorological measurement system are controlled according to the ambient temperature to prevent icing.
Flashing obstruction light control: A flashing obstruction light is installed at the end of each blade to illuminate at night.
The cabin fan controls the ambient temperature inside the cabin.
(4) Electric pitch control system
The pitch control system includes a motor, driver, and main control PLC on each blade. The PLC communicates with the main control system of the turbine through the CAN bus and is the pitch control unit in the wind power control system. The pitch control system has a backup DO feathering control interface.
(5) Speed-increasing gearbox system
The gearbox system is used to increase the wind turbine speed to the normal operating speed range of the doubly-fed generator. It is necessary to monitor and control the gear oil pump, gear oil cooler, heater, lubricating oil pump, etc.
When the gear oil pressure is lower than the set value, the gear oil pump starts; when the pressure is higher than the set value, the gear oil pump stops. When the pressure exceeds the limit, an alarm is issued and the shutdown procedure is executed.
Gear oil cooler/heater controls gear oil temperature: when the temperature is lower than the set value, the heater starts; when the temperature is higher than the set value, the heater stops. When the temperature is higher than a certain set value, the gear oil cooler starts; when the temperature drops to the set value, the gear oil cooler stops.
The lubricating oil pump is controlled so that it starts when the lubricating oil pressure is lower than the set value and stops when the oil pressure is higher than the set value.
(6) Yaw system control
Based on the current nacelle angle, the measured low-frequency average wind direction signal value, and the current operating status and load signal of the unit, the CW (clockwise) and CCW (counterclockwise) motors are adjusted to achieve automatic wind and cable unwinding control.
Automatic wind alignment: When the unit is in operation or standby mode, the CW and CCW motors are adjusted according to the deviation value of the nacelle angle and the measured wind direction to achieve automatic wind alignment. (Yawing is performed at the set yaw speed, and the operating status of the yaw motor needs to be monitored.)
Automatic unmooring control: When the unit is in a suspended state, if the nacelle twists more than 720 degrees in a certain direction, the automatic unmooring procedure is initiated; or when the unit is in operation, if the twist exceeds 1024 degrees, the unmooring procedure is implemented.
(7) Communication of high-power converters
The main controller communicates with the converter via the CANOPEN communication bus. The converter performs grid-connection/disconnection control, generator speed regulation, active power control, and reactive power control.
Grid connection and grid disconnection: According to the master control instructions, the converter system excites the generator rotor and controls the generator stator output power to be in the same frequency, phase and amplitude, and then drives the stator output contactor to close to achieve grid connection; when the generator power is less than a certain value for several seconds or when the wind turbine or the grid has an operating fault, the converter drives the generator stator output contactor to open to achieve grid disconnection of the unit.
Generator speed regulation: When the unit is running below the rated load after grid connection, the generator speed is controlled to make the unit run on the optimal λ curve. The wind turbine is used as an anemometer to measure the real-time torque value and adjust the unit to the optimal state of operation.
Power control: When the unit enters the constant power zone, it maintains the unit's output power according to the communication command with the frequency converter.
Reactive power control: Reactive power control or power factor adjustment is achieved through communication commands with the frequency converter.
(8) Safety chain loop
The safety chain loop is independent of the main control system and executes emergency shutdown logic in parallel. All related drive loops are powered by backup batteries to ensure reliable system operation in emergency situations.
V. Conclusion
Wind power, as a green and renewable energy source, has received strong support from national industrial policies in recent years. The establishment of the wind power division by Keyuan to conduct research on wind power control systems is a direct result of this support. While my country has made significant progress in the manufacturing technologies of wind turbines, gearboxes, and blades, key technologies for control systems, including variable speed constant frequency control systems, pitch systems, main control systems, grid connection systems, and integrated wind farm monitoring systems, still lag considerably behind those of foreign countries. Currently, almost all of these technologies are imported, and foreign manufacturers even impose restrictions on certain key technologies. Therefore, from the perspective of breaking foreign technological monopolies, ensuring national power security, and sharing the huge wind power market, the successful development of the WPCS wind power control system will have immense practical significance.
