提出了一种HVDC改进型在线模糊神经控制器以提高交直流互联系统的暂态稳定性。在该控制器的设计中，采用了模糊逻辑控制和人工神经网络技术相结合的方法以实现在线定电流控制，并利用了NETOMAC软件的参数优化功能对控制器的重要参数进行了离线优化，使其控制性能更优。仿真结果表明该控制器有效地抑制了交直流系统的有功功率振荡，改善了系统的功角特性，且具有较好的鲁棒性、自适应性及动态性能。

The additional controller in HVDC system can improve the power system stability. According to multi-infeed HVDC transmission system, this paper design the additional controller of HVDC system with the nonlinear control theory. The control law which we get consider the influence of two additional controls of DC system. It can improve the system stability to a great extent. The simulation results also testify the validity of it.

In this paper, a fault current limiter (FCL) with series compensation is proposed. It is composed of a limiting reactor and a compensation capacitor that is parallel with a by-pass reactor controlled by GTO. The FCL can not only control fault current, but also perform series compensation. The good performance of this device is proved by simulation, it will be a practical protection device for power systems in the future.

To improve the performance of High Voltage Direct Current (HVDC) transmission system, the constant reactive current control is used to take the place of the traditional constant firing angle control at the inverter. This paper presents a method of controller design, which is based on feedback linearization in the nonlinear systems and Variable-Structure control theory in the linear system. It can be testified by simulation that the new controller can not only improve the characteristic of DC system, but also enhance the voltage stability of AC system.

Abstract A novel nonlinear emergency control method for HVDC transmission systems is presented in this paper. First, an observation decoupled state space model of AC and DC interconnected power systems, which allows estimation or computation of the state components from local measurements, is developed. Secondly, the nonlinear control rules of HVDC links are derived using optimal-variable-aim strategy (OVAS), which not only improves the first swing stability, but also effectively damps the subsequent power oscillation. Finally, the simulation results of a three-machine six-bus system show that the proposed method can enough use the capabilities of fast response and short-time overload of HVDC links to improve the transient stability of power systems.