Moog pitch control valve features embedded motion control capabilities

Moog has developed a unique “pitch control valve” that uses the latest digital technology for position control for wind turbines for MADE Tecnologías Renovables S.A.  This intelligent servovalve has been enhanced with digital communication and embedded motion control capabilities that enables it to close the position loop within the valve.  This axis control functionality is a revolutionary development. It enables performance, reliability, remote diagnostics, and process control in one device, which is functionality that could never be achieved with conventional valve technology. The intelligence embedded in this device also enabled the customer to eliminate the cost and complexity of the external controller (PLC).

Pitch control of a wind turbine is a challenging control problem to address for many reasons including the need for high performance, ability to handle extreme environmental conditions, and accommodation of safety considerations. Wind Turbines generate power based on harnessing wind force. They operate 24 hours a day in large installations with minimal personnel manning many units. The motion control requirements are complex due to the need to achieve precision control of the pitch on each of the 3 blades.  Each blade has completely different and changing reaction forces depending on their up or down position. Safety and reliability are also critical due to the large size and height of the units.

The motion control system Moog developed in collaboration with MADE needed to address different technical challenges.  Position control was a challenge as the reaction forces on the blades changes depending on their position. In addition, for safety concerns, the blades had to return to the home position in the case of a serious fault.  The motion control and data transmission also had to be reliable even in extreme vibration and temperature situations. The customer also required remote self-monitoring to reduce down time and accommodate the need to climb the wind turbine tower to detect a fault.

The product developed for this customer is part of Moog's new hydraulic valve platform, the Axis Control Valve with CAN-bus interface (D636 and D637 series).  The product is based on a proven servovalve design that has been enhanced with digital communication capabilities and the ability to close the position loop within the devices.  For the “pitch control servovalve”, Moog also developed flexible configuration software for axis control that was designed specifically for the customer.  Moog is also supplying prototypes of its Radial Piston Pump (RKP), which will be in a dual pump arrangement on the same shaft for cost savings.

Other features of the Moog solution include a fail-safe system in the valve to synchronize the movement to “home position” in the case of a PLC fault, thereby ensuring maximum safety protection. The Moog Valve Configuration Software was critical to enabling the customer to adjust the pitch of the blades to reach the highest performance. This also enabled very powerful control strategies such as “active dampening” to reduce oscillation that is destructive to the integrity of the shaft. This will increase the power output, ensure the longevity of the system, and reduce maintenance costs.

Remote diagnostics and the ability to make adjustments “on the fly” were critical to improving operational effectiveness of the wind turbine.  In addition, digital valves offer a “plug and play” benefit where every new valve can be identical to its predecessor with no need for the PID adjustments common in traditional valves. This makes startup easier and more predicable and facilitates the development of new generation turbines.

"Our relationship with MADE has enabled us to design and build an exciting new solution that offers numerous advantages over the traditional approach, " said Joseph Dyer, Regional Sales Manager, Moog. “We are confident that we will continue to work with the customer to achieve even higher performance and optimization of the process due to the flexibility and benefits of this new servovalve platform.”

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