Research On Response-Driven Adaptive Load Shedding Control Facing To Transient Voltage/Frequency Recovery Criterion Requirement

With multi-infeed HVDC in the receiving-end power grid,the significant increase in the proportion of new energy units,and the elimination of a large number of traditional fossil energy synchronous units,the degree of power electronics in the receiving-end power grid is continuously deepening,and the level of the system short-circuit ratio is declining.At the same time,with the continuous development of the national economy,the demand for electric energy continues to increase,and the load of induction motors in the power grid increases significantly.When a large disturbance fault occurs,the system is prone to insufficient dynamic reactive power support,causing multi-modal voltage evolution problems such as transient voltage delayed recovery or transient voltage instability and other problems.On the other hand,the inertia level of the receiving-end system is weakened,and the overall primary frequency regulation capability of the synchronous unit of the system is reduced.The system is also prone to insufficient active power support due to large disturbances,causing problems such as transient frequency delayed recovery or transient frequency instability.In this regard,the power grid puts forward a more precise and strict safety recovery requirement of "safety threshold-recovery time" for the voltage/frequency recovery after the disturbance.The voltage/frequency safety control method required by the grid transient voltage recovery criterion(TVRC)/frequency recovery criterion(transient frequency recovery criterion,TFRC)is particularly important.First,calculate the trajectory offset based on the TVRC/TFRC requirements and real-time voltage/frequency evolution trajectory,analyze the characteristics of the transient voltage/frequency time series trajectory,quantify the offset between the timing trajectory and the safety boundary and the offset between the timing trajectory and the initial state,and take the time accumulation of the offset into account to study the voltage/frequency safety evaluation index oriented to the timing trajectory,which can provide the evaluation basis for the voltage/frequency safety degree and safety control of the receiving-end system.Secondly,a response-driven adaptive load shedding control strategy oriented to TVRC requirements is proposed.Based on fuzzy control theory,a TVRC-oriented intelligent adaptive under voltage load shedding(UVLS)controller is developed,and logical inference rules for preventing over-or under-shedding problems are introduced.Load shedding controllers deployed at load buses can perform the "judgment-decision-control" closed-loop load shedding action according to the local voltage information independently;In order to further improve the performance of load shedding control,an optimal tuning model of controller parameters is proposed with the constraint that voltage recovery meets TVRC requirements and the goal of minimizing the cost of load shedding control.The particle swarm optimization(PSO)is used to solve the model;In the last,the load shedding controllers on each load station jointly constitute an optimized fuzzy adaptive load shedding control strategy that responds to TVRC requirements.Simulations results verify that the proposed load shedding strategy can effectively solve the multiform transient voltage evolution problem,promote the voltage recovery after the disturbance to meet the TVRC requirements,and have strong robustness and applicability.Finally,a response-driven adaptive load shedding control strategy oriented to TFRC requirements is proposed.A TFRC-oriented intelligent fuzzy logic under frequency load shedding(UFLS)controller is developed;In terms of control performance,a controller parameter optimization tuning model with the constraints of frequency recovery meeting TFRC requirements and the goal of minimizing the cost of load shedding control was constructed,and the controller parameters were optimized by applying beetle swarm optimization(BSO);Eventually,the optimized load shedding controllers deployed at load buses constitute an optimal fuzzy adaptive load shedding control strategy in response to TFRC requirements,which can achieve frequency recovery to meet TFRC requirements with a smaller cost of load shedding control.The validity and applicability of the proposed load shedding strategy are verified through the simulation analysis.