Wind Turbine Pitch Control
A wind turbine pitch control system can change incidence of rotor blades in a wind power generation system based on real-time wind speed for the purpose of adjusting output power, achieving higher utilization efficiency of wind power and providing protection for rotor blades. When wind speed is not higher than the rated speed, the blade incidence stay near the angle 0° (highest power point), which is similar to that of a generator with constant pitch, generating an output power that changes along with wind speed. When wind speed is higher than the rated speed, the pitch control mechanism changes blade incidence so that the output power of generator is within the allowed range.
Typically a wind turbine pitch control system is built with a controller, pitch control mechanisms, a backup power supply, and a feedback module monitoring generator output power. High performance MCUs or DSCs are often selected as the controllers of pitch control systems. They are responsible for giving instructions to pitch control mechanisms based on real-time wind speed, preset power rating, pitch information, and output power signal of generator. Pitch control mechanisms are commonly made up of rotary encoders, gate drivers, IGBT modules and servo motors. Each motor blade needs a single control mechanism, which means three mechanisms in total are required. After the instructions given by controller are received, the gate drivers, IGBT modules of these mechanisms drive their associated motors to change blade incidence. Meanwhile, the real-time pitch information is sent back to controller by rotary encoders. Feedback module is composed of voltage sensor and current sensor which the collect voltage and current signals from generator and send to controller. In order to feather the blades in the event of an emergency situation, backup power is needed. Backup power can be implemented with batteries, ultra-capacitors, or even a hybrid solution offering the best of both options.