含储能型虚拟同步发电机的直驱风机并网系统自适应协调阻尼控制策略

储能型虚拟同步发电机(VSG)的灵活控制特性能够为风电并网系统提供有效的频率和电压支撑,然而系统振荡特性会受到一定程度的影响,同时风电时变出力特性导致的运行点变化也将使得定参数阻尼控制表现出适应性不足的问题.为此,提出了适应风电出力时变特性的自适应协调阻尼控制策略.首先,在风电并网系统状态空间模型的基础上推导线性变参数模型,以直驱风机的有功功率为调度变量,根据稳定域确定运行空间范围;然后,利用间隙度量对运行空间进行划分,确定各子运行空间的典型运行点并将其作为多胞形顶点,建立调度增益与系统运行工况以及控制器的映射关系;最后,针对不同频率振荡模式协调设计自适应控制器.测试系统的仿真结果表明,所设计的自适应协调阻尼控制器不仅能够同时阻尼含储能型VSG并网系统中的次同步振荡和低频振荡,也能在风电出力大范围时变工况下保持良好的阻尼水平.

Adaptive coordinated damping control strategy for grid-connected direct-driven wind turbine system with energy storage-based virtual synchronous generators

The flexible control characteristics of the energy storage-based VSG(Virtual Synchronous Generator) can provide effective frequency and voltage support for the grid-connected wind power system. However, the system oscillation characteristics will be affected to some extent, and the change of operation point caused by the time-varying output characteristics of wind power will also cause insufficient adaptability of the fixed parameter damping control. Therefore, an adaptive coordinated damping control strategy is proposed to adapt to the time-varying characteristics of wind power output. Firstly, the linear parameter varying model is derived based on the state space model of grid-connected wind power system. The active power of direct-driven wind turbine is taken as the scheduling variable and the operation space range is determined according to the stability region. Then, the operation space is divided according to the gap metric, the typical operation points of each sub-operation space are determined and taken as the vertices of polytope, and the mapping relationship between the scheduling gain and the system operation conditions and the controller is established. Finally, an adaptive controller is designed for different frequency oscillation modes. Simulative results of the test system show that the adaptive coordinated damping controller can not only damp the sub-synchronous oscillation and low frequency oscillation simultaneously in the grid-connected energy storage-based VSG system, but also maintain a good damping level under a wide range of time-varying operating conditions of wind power output.