基于虚拟阻抗优化的VSG暂态功角稳定自适应控制策略

Improvement of transient stability performance of VSG considering power angle stability and fault current limiting

在电网短路故障发生的情况下,虚拟同步发电机系统不仅会发生暂态功角失稳,同时还可能会出现过流。为了提升虚拟同步发电机的暂态功角稳定性及故障电流限制性能,首先建立了包含电压和电流控制环、虚拟阻抗及功率控制环结构的虚拟同步发电机系统的总体控制结构,给出了虚拟阻抗功率模型建立的理论依据。对无功功率控制环路恶化暂态功角稳定性,提出了设置电压增量自由控制支路来实现提高暂态功角稳定性的方法。其次,在无功功率控制环路及电压增量自由控制支路的共同作用下,对“不考虑切除故障”和“考虑切除故障”两种不同的运行工况,提出了能够同时满足暂态功角稳定性和故障电流限制的虚拟阻抗优化方法。最后提出了虚拟同步发电机的暂态功角失稳控制和故障电流限制的自适应控制算法,以满足实际运行工况的需求,通过Simulink仿真模型验证了所提自适应控制策略的有效性和可行性。

In addition to transient power angle instability,the virtual synchronous generator system may also experience overcurrent in the event of a grid short circuit fault.In order to improve the transient power angle stability and fault current limiting performance of VSG,firstly,the overall control structure of virtual synchronous generator system including voltage and current control loop,virtual impedance and power control loop structure is established in this paper,the theoretical basis for establishing a virtual impedance power model is provided.Due to the activation of reactive power control loop,transient power angle stability will be reduced,a method of improving the power angle curve by setting the free control branch of the voltage increment is proposed.Secondly,with the combined effect of the reactive power control loop and the voltage increment free control branch,a virtual impedance optimisation method that can simultaneously satisfy transient power angle stability and fault current limitation is proposed for two different operating conditions,namely“without considering fault removal”and“considering fault removal”.Finally,adaptive control algorithms for transient power angle instability control and fault current limitation of virtual synchronous generators are proposed to meet the requirements of real operating conditions.The validity and feasibility of the control strategy proposed in this paper are verified by the simulation model.