Enhanced Control and Operation of Doubly-Fed Induction Generator Based Wind Farm during Network Unbalance

本提案旨在研究系统控制和基于双馈感应发电机（DFIG）的风电场的操作，连接到传输系统或嵌入在配电系统中，当网络电压是不平衡的。不平衡电压可以是由不对称交流故障引起的大的瞬态不平衡，也可以是小的稳态不平衡。该项目将首先开发一个数学模型，其中包括一个DFIG和两个背靠背连接的转换器在不平衡电源。将检查不平衡的网络电压对DFIG和相关转换器的操作的影响。本项目将进一步探索双馈发电机在不平衡网络电压下可采用的策略，以提供增强的操作，例如改善系统在不对称故障期间和之后的操作和恢复，保持平衡的定子电流，最大限度地减少双馈发电机的电转矩脉动或对网络电压的再平衡做出贡献。在网络电压不平衡期间控制DFIG系统的方法，通过提供定子/转子电流的精确控制，如果需要的话，不对称的有功和无功功率输出，然后将进行研究。将进行实验测试，以验证所提出的控制策略。

This proposal intends to study the system control and the operation of wind farms based on Doubly-Fed Induction Generators (DFIG), connected to either a transmission system or embedded within a distribution system, when the network voltage is unbalanced. The unbalanced voltage can either be a large transient unbalance caused by asymmetric AC faults or a small steady-state unbalance. The project will first develop a mathematical model which includes a DFIG and two back-to-back connected converters under unbalanced supply. The impact of unbalanced network voltage on the operation of the DFIG and the associated converters will be examined. This project will further explore strategies that can be employed by the DFIG under unbalanced network voltage for providing enhanced operation such as improving the system operation and recovery during and after asymmetric fault, maintaining a balanced stator current, minimising DFIG electric torque pulsation or making a contribution to the rebalancing of the network voltage. Methods for controlling DFIG systems during network voltage unbalance, by providing precise control of the stator/rotor current and if required, the asymmetric active and reactive power outputs, will then be investigated. Experimental tests will be carried out to validate the proposed control strategy.