虚拟同步机孤岛并联系统暂态同步稳定性分析

针对虚拟同步机孤岛并联系统暂态失稳机理不明且传统等面积法则定量计算保守性强的问题，提出了一种考虑阻尼缩放的改进等面积法则。该方法运用等面积法则，将阻尼项抵消的不平衡功率缩放为对功角可积项，可定量计算虚拟同步机控制参数对并联供电系统极限切除角和极限切除时间的影响。研究结果表明，虚拟同步机的虚拟阻尼对暂态稳定性影响较大。虚拟阻尼与极限切除角和极限切除时间呈正相关；虚拟惯量与极限切除角呈负相关，与极限切除时间呈正相关，在系统容量充足的情况下应优先考虑提升虚拟阻尼。另外，初步探索了计及虚拟同步发电机过流保护的多机并联系统暂态同步稳定性研究思路，并分析了所提方法在多机系统中的适用性。最后，基于PSCAD/EMTDC仿真平台验证了理论分析和所提方法的正确性。

Transient synchronization stability analysis of a virtual synchronous machine isolated island parallel system

There is a problem that the transient instability mechanism of an isolated parallel system of a virtual synchronous machine is unclear and the traditional equal area rule is conservative in quantitative calculation. Thus this paper proposes an improved equal area rule considering damping scaling. This method uses the equal area rule to scale the unbalanced power offset by the damping term into an integrable term of opposite angle. The influence of the control parameters of the virtual synchronous machine on the critical clearing angle (CCA) and critical clearing time (CCT) of the parallel power supply system can be calculated quantitatively. The results show that the virtual damping of the virtual synchronous machine has a great influence on transient stability. The virtual damping is positively correlated with the CCA and the CCT; also the virtual inertia is negatively correlated with the CCA and positively correlated with the CCT, and the virtual damping should be given priority when the system capacity is sufficient. The research idea of the transient synchronization stability of a multi-machine parallel system with VSG overcurrent protection is preliminarily explored, and the applicability of the proposed method in multi-machine systems is analyzed. Finally, based on the PSCAD/EMTDC simulation platform, the correctness of the theoretical analysis and the proposed method is verified.