可变频率变压器的最大功率传输控制策略

可变频率变压器（VFT）是一种能连接异步电网的新型灵活交流输电系统设备，其可传输功率的容量是重要的性能指标。针对传统控制策略未考虑转差率增大可能导致转子绕组超过额定容量的问题，对不同的转差率和定子无功功率情况下定子有功功率最大值进行研究；详细研究了采用串联变换器的VFT系统运行特性；对不同转差率进行了详细的工况分析。推导出最优定子无功功率给定值与转差率、额定视在功率和实际吸收无功功率之间的数学关系，并提出了VFT的最大功率传输（MPT）控制策略；通过硬件在环实验平台验证提出的MPT控制策略的有效性。实验结果表明，所提MPT控制策略能有效提高VFT的可传输功率，实现VFT的最大功率传输。

Maximum Power Transfer Control Strategy for Variable Frequency Transformer

Variable frequency transformer (VFT) is a new type of flexible AC transmission system equipment to achieve the interconnections of asynchronous grids, whose transmittable power capacity is an important performance indicator. In view of the problem that the traditional control strategy does not consider the rotor winding’s overloading caused by the increase of slip rate, a study is conducted on the maximum stator active power under different slip rates and stator reactive power, and the operation characteristics of a VFT system based on series converter are investigated. The detailed working conditions are analyzed for different slip rates. The mathematical relationship between the optimal stator reactive power reference and the slip rate, and the rated apparent power and the actual absorbed reactive power is derived, and the maximum power transfer (MPT) control strategy for VFT is proposed. A hardware-in-loop (HIL) experimental platform is established to verify the effectiveness of the proposed MPT control strategy. The experimental results show that the proposed MPT control strategy can effectively increase the transferable power capacity of VFT and realize the maximum power transfer of VFT.