Modelling and Analysis of Electromagnetic Time Scale Voltage Variation Affected by Power Electronic Interfaced Voltage Regulatory Devices

This paper establishes an instantaneous voltage model to illustrate the dynamic characteristics of grid voltage in electromagnetic time scale affected by power-electronic interfaced voltage regulatory devices with two typical categories of control systems, i.e. power-current cascading control and power synchronization control, exemplified by the STATCOM and virtual synchronous condenser (VSCON) respectively. In this paper, a linearized instantaneous voltage model is firstly established to analyze the impact paths of control loops in the STATCOM and VSCON. Based on the model, the dynamic process of grid voltage is divided into three stages. Various factors on the dynamic process of grid voltage are analyzed, especially cascading control loops prior to the functioning of AC voltage control. Moreover, stiffness characteristic is proposed to evaluate the effects of power electronic interfaced voltage regulatory devices with different control structures. In addition, the effectiveness of the stiffness compensation based on the VSCON is validated by the study cases.