针对交直流系统中影响暂态稳定的主要因素,即电磁转矩和机械转矩之间不平衡的问题,结合直流传输功率可进行快速调节的特点,提出了将直流功率调制和汽门开度进行协调控制的方案,以提高交直流系统的暂态稳定性。由于交直流系统为多输入多输出的非线性系统,控制方案采用了非线性系统状态反馈精确线性化理论和线性最优控制理论相结合的设计方法。用一个典型的交直流并联系统进行数字仿真的结果表明,这种协调控制既可以有效地提高交直流系统的暂态稳定性又可以利用HVDC的短时过载能力为突然产生功率严重缺额的地区提供紧急功率支援。
The imbalance between electromagnetic torque and mechanical torque of each synchronous machine is the main factor which affects transient stability in the AC/DC transmission systems, and the DC power can be regulated rapidly. Thereby, combining the control of valve opening and DC power modulation, we proposed a coordinated control strategy to improve transient stability. According to the characteristic of system model, namely, a nonlinear system with multi-input and multi-output, the control strategy was designed based on feedback linearization of nonlinear system theory and optimal control theory of linear system. The validity of the coordinated control method was verified in a typical AC/DC parallel hybrid transmission system.