Application of active thermal control methods for improving the thermal cycling performance and service lifetime of the machine-side converter of an airborne wind energy generator

Abstract

High altitude wind systems are an upcoming wind power technology which extracts power from very high altitudes. In it, pumping cycle airborne wind energy system with reel out and reel in cycles undergo tremendous thermal stress in machine side converter during operation and consequently, the lifetime of the converter is adversely affected. In order to mitigate this problem, active thermal control methods: variable switching frequency control, variable coolant flow, variable DC link and direct axis current injection methods are used.

The working of the given airborne wind energy system is explained first and then the method of implementation of the four active thermal control methods into the system model is also discussed. The analysis is done individually for each of the active thermal control methods and the corresponding improvement in thermal characteristics is compared with the default model. The analysis also studies on how the lifetime of the converter is affected with the implementation of each of the active thermal control methods and also for a hybrid model which is a combination of active thermal control methods. The results show an improvement in the lifetime of the converter for all active thermal control methods with the best lifetime recorded for the hybrid model which considers both long term and short term thermal cycles.