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Hybrid Control of Multiple Input-Single Output Control System for Converter Cooling Systems in Wind Turbines

IP.com Disclosure Number: IPCOM000212863D
Original Publication Date: 2011-Nov-30
Included in the Prior Art Database: 2011-Nov-30
Document File: 2 page(s) / 124K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

Modern wind turbines utilize converter systems in order to speed up the generator and thus, increase efficiency of the power plant. Moreover, the usage of these converter systems allows for variable speed turbines and more energy can be collected. Another positive side effect is the reduction of acoustic noise generated by the fan. High temperatures generated within the converter affect the life time of the unit. Therefore, the generator needs to be cooled and equipped with appropriate temperature control systems. Due to its complexity, the converter system is a cost intensive component of the wind power plant.

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Hybrid Control of Multiple Input-Single Output Control System for Converter Cooling Systems in Wind Turbines

Idea: Lennart Weiss, DK-Brande; Jens Due, DK-Brande

Modern wind turbines utilize converter systems in order to speed up the generator and thus, increase efficiency of the power plant. Moreover, the usage of these converter systems allows for variable speed turbines and more energy can be collected. Another positive side effect is the reduction of acoustic noise generated by the fan. High temperatures generated within the converter affect the life time of the unit. Therefore, the generator needs to be cooled and equipped with appropriate temperature control systems. Due to its complexity, the converter system is a cost intensive component of the wind power plant.

Recent converter cooling systems for wind power turbine generators utilize a circulating water cooling system. The temperature of the fluid, in this case water, is controlled by application of a motor valve and a variable speed fan. Consequently, the motor valve and the fan are used concurrently to control the temperature of the water. These constitute two different control systems which are coupled together by the actual systems. The problem with this solution is that the motor valve and the fan can introduce disturbances into each other. For example, when the fan speed is changed, the motor valve reacts accordingly and vice versa. These disturbances can cause oscillations and instability of the control system. Further, there is no direct feedback of the motor valve position. Thus, the cooling capabilities are not optimally used, which result in the fan operating at higher speeds than necessary since the valve is never fully opened.

In order to increase the efficiency of the converter cooling systems of wind turbines, a novel hybrid control strategy is proposed, which can be used for noise reduction as well as for improving the life time of the converters. Figure 1 depicts a schematic view of the proposed cooling strategy. This cooling strategy is based on two separate proportional-integral-derivative controllers (PID), which are used to calculate an error based on the difference between a measured process variable and a desired value. According to the error value, the controller is able to adjust process control inputs in order to minimize the error. As proposed, one PID controller is used controlling the fan and the other for controlling the motor valve. The input value of both controllers is the desired temperature value for the converter cooling fluid. The "Hybrid Control Strategy" block in the diagram is used to determine which of the both PID controllers need to be active in a c...