A Study of Transient Stability and Stabilization Control of Power System Including Wind Generators

本文首先对包括风力发电机在内的电力系统在对称和非对称短路故障情况下的暂态稳定性进行了仿真分析。仿真中采用了单质量和双质量两种轴系模型，分析了轴系建模对风力发电机暂态稳定性的影响。仿真结果表明，风力发电机组系统的暂态稳定很大程度上依赖于轴系的建模。对于相同的故障条件，双质量模型给出的结果是不稳定的，而单质量模型给出的结果是稳定的。发电机与风力机之间轴的弹簧常数较大的风力发电系统在电力系统故障时具有暂态稳定性。发电机和风力机总惯性常数较大的风力发电系统在电力系统故障时暂态稳定。风力发电系统的惯性常数越大，在电力系统发生故障时，风力发电系统的暂态稳定性越好。在电力系统仿真中，为了简单起见，风力发电机通常用单质量模型表示。然而，从上述结论可以清楚地看出，为了进行精确的暂态稳定分析，风力发电机需要用双质量模型来表示。其次，分析了双馈飞轮发电机（双馈异步发电机，DASM）风力发电系统稳定的新方法。PSCAD/EMTDC的各种仿真结果表明，DASM无功补偿可以有效地防止风电机组短路故障后电压崩溃。并对风力机纵摇控制与所提方法进行了对比研究。后者明显优于前者，这一点得到了证实。可以说，与传统的螺距控制系统相比，DASM可以作为一种更有效的稳定电力系统的方法。研究还发现，DASM可以为风力发电机在稳态状态下提供局部领先的无功补偿。并对风电功率随机波动时的多台风力发电机组系统进行了仿真。研究中使用了两种典型的风速模式。结果表明，当风电功率波动时，DASM对风电场输出功率和终端电压的平滑变化是有效的。总而言之，仿真结果表明，DASM可以有效地减小网络中较大的电扰动和强阵风对系统的影响。仿真结果也表明了DASM在稳定状态下为风力发电机提供局部超前无功补偿的有效性。少

In this study, firstly simulation analyzes of transient stability of power system including wind generator during symmetrical and unsymmmetrical short circuit faults are performed. Two shaft system models are used for the wind generator in the simulations, which are one-mass and two-mass shaft models, and an effect of shaft system modeling on the transient stability is analyzed. Based on the simulation results, it is concluded that the transient stability of wind generator system is strongly dependent on the modeling of the shaft system. The two-mass shaft model can give an unstable result though the one-mass model gives a stable result for the same fault condition. Wind generator system with large spring constant of the shaft between generator and wind turbine is transiently more stable during power system fault. Wind generator system with large total inertia constant of generator and wind turbine is transiently more stable during power system fault. Wind generator system having large … More inertia constant of generator is transiently more stable during power system fault. In power system simulations, wind generators are often expressed by a one-mass model for simplicity. However, it is clear from the above conclusions that wind generators need to be expressed by a two-mass model in order to perform exact transient stability analysis.Next, a new way of stabilization of the wind generator system with doubly-fed flywheel generator (doubly-fed asynchronous machine, DASM) is analyzed. Various simulation results by PSCAD/EMTDC show the effectiveness of preventing the voltage collapse of the wind generators after a short circuit fault with the reactive power compensation from DASM. Comparison studies are also performed between the wind turbine pitch control and the proposed method. The apparent superiority of the latter to the former is validated. It can be said that DASM can be used as a much more effective way to stabilize the power system as compared with conventional pitch control system. It is also found that DASM can be used to provide locally the leading reactive power compensation to the wind generators in the steady state. Simulation is also done on multiple wind generator system when wind power fluctuates randomly. Two typical types of wind speed patterns are used in the study. Both results show the effectiveness of DASM on smoothing variations of output power and terminal voltage of the wind farm when wind power fluctuates. All in all, simulation results show that DASM can be used to minimize the influence to the system under large electrical disturbances in the network and under a severe wind gust effectively. Simulation results also show the effectiveness of DASM in providing locally the leading reactive power compensation to the wind generator in steady state. Less