Research On Controlled Islanding Scheme For AC/VSC-HVDC Systems With Multiple Constraints

With the continuous expansion of the grid and the formation of cross-regional grid interconnection models,the dynamic stability of power systems is being seriously challenged.When the power system is seriously faulty,the splitting control is the last line of defense to prevent the spread of the fault or even the collapse of the whole network,which is of great significance to the safe and stable operation of the system.The traditional splitting control is the out-of-step islanding with a simple structure and convenient configuration.However,with the formation of large-scale cross-regional interconnected power grids,the out-of-step islanding based solely on the local fault information of the grid is obviously no longer sufficient.At this time,with the maturity of wide-area measurement technology and the large-scale popularization of wide-area measurement devices,the controlled islanding that can detect the whole network information in real time and perform global control of the power grid becomes the research hotspot of the current problem of splitting.Previous studies on controlled islanding problems are mostly limited to power networks with pure AC systems.However,with the rapid development of flexible HVDC transmission technology and the advantages of VSC-HVDC systems in asynchronous grid interconnection,this paper proposes a new controlled islanding problem model with AC/VSC-HVDC hybrid grid.The characteristic of the model is that the VSC-HVDC system can independently control the active power and reactive power to realize the interconnection between the asynchronous subsystems after splitting,which effectively reduces the generator tripping and load shedding and decreases economic costs.In order to solve the model,a new algorithm based on constrained spectral clustering is proposed.This method transforms the splitting boundary searching problem into the optimal graph partition problem which is easy to solve,and the original network does not need to be simplified.Meanwhile,this method can satisfy kinds of related constraints to ensure the operation of the power system,and realize power exchange between subsystems formed after splitting.Finally,through the simulations of the improved IEEE 39-bus system and the practical Xiamen power system,the accuracy and rapidity of the proposed method in finding the optimal islanding solution are verified.