Research On Modeling And Coordinated Control Strategy For Virtual Power Plant To Participate In Emergency Control

With the integration of a high proportion of renewable energy and large capacity high voltage direct current links,the stability characteristics of the power system are changing significantly.The system inertia level and the frequency regulation ability of the receiving-end grid are significantly reduced,increasing the risk of large frequency deviation or even instability under high-power loss disturbances such as high-voltage direct current(HVDC)blocking.Emergency control is important to prevent power outages.The conventional emergency load shedding cuts off high voltage outlets or the substation,so it severely impacts residents’ lives,and its cost is high.The practical application of large-scale load shedding makes society intolerable.The security and stability control of the power grid is facing severe challenges,and new fast regulation resources are urgently needed.At the same time,distributed energy resources(DERs)on the demand side,which include distributed generation and various new loads,have huge power regulation potential.The aggregation control of DERs and interaction with the bulk system can become a new resource for power grid security and stability control,and it is important for the digital and intelligent development of power systems.The virtual power plant(VPP)can efficiently manage DERs and interact with the grid as a controllable whole.The flexible and fast regulation ability of VPP can not only participate in the power balance adjustment but also be a new emergency control resource,bringing the massive controllable DERs into the grid security defense system.However,there are many gaps in VPP participation in emergency control,including the simulation and analysis of characteristics,the determination of control boundaries,and the coordinated control strategy.How to construct a new stable control structure with controllable DERs is still an open problem.Therefore,this paper aims to bring VPP into the security and stability control system of the power grid,focusing on the construction of modeling and analysis tools and coordinated control for emergency control.In this paper,the hierarchical modeling and refined production simulation of VPP,the quantitative evaluation of VPP emergency power regulation capability,and the coordination strategy of emergency frequency control considering VPP are studied.The main work is as follows.(1)Aiming at the modeling requirements of equipment characteristics and management and control characteristics of VPP,a VPP short-term refined production simulation method,and system covering characteristics modeling and software is proposed and implemented,which provides a tool for DERs characteristic analysis and grid stability control effect analysis.Firstly,based on the VPP characteristics and its participation in stability control demand analysis,the key technologies of VPP refined simulation are given.Then,a general VPP simulation architecture is designed to simulate device characteristics and control algorithms.A heterogeneous DERs device layer modeling method covering physical characteristics,environmental and user behavior impact is proposed,and a control algorithm simulation method adapted to the VPP hierarchical management architecture is proposed.Finally,based on modularity,universality,and openness principles,the VPP model implementation class family and the co-simulation architecture are designed using an object-oriented method.The case shows that the proposed VPP refined modeling method can realize the simulation of the behavior characteristics of DER individual device and DER cluster,and the effect of participating in angle stability control,providing a simulation platform for the effective evaluation and control strategy design of VPP participating in power grid stability control.(2)Aiming at the requirements of determining VPP emergency power regulation capability for participating in emergency control,a quantitative evaluation method and online implementation process of VPP emergency power regulation capability considering both physical state and user behavior are proposed,which provides credible VPP regulation boundaries for grid control decision-making.Firstly,the connotation of VPP emergency power regulation capability is clarified from the demand to participate in emergency control.A quantitative evaluation method is proposed considering the regulation capacity and duration for VPP emergency power regulation capacity and its online evaluation idea.Then,an evaluation model of the DER individual device considering both physical state and user behavior is constructed,and the capability aggregation and the complete evaluation process of the VPP layer are proposed.Finally,based on the principle of realizing the evaluation modularization,the VPP emergency power regulation capability evaluation module is developed,which can be embedded into the refined production simulation system or electromechanical transient simulation software.The case shows that the proposed evaluation method can consider the DER device’s state transition and response constraints and realize the accurate evaluation of the individual device and VPP regulation capacity.Setting a reasonable evaluation period can ensure that the adjustment ability evaluation error and reduce the computational burden of evaluation.(3)Aiming at the application requirements of VPP participating in frequency emergency control,a method for multiple resources emergency frequency control coordinated strategy considering VPP in the receiving-end grid is proposed,which realizes frequency stability control with low cost by fast power regulation of DERs on the demand side.First,based on the characteristics of the VPP control structure and online pre-decision,a bi-level optimization framework is constructed,which are emergency frequency control decision making and the control instruction allocation of VPP.Then,the VPP response process model and its control cost model are established based on its response characteristics.Considering DC emergency power support,emergency load shedding,and VPP coordination participation,the emergency frequency control optimization model is established to minimize the control cost.A decision solving method based on electromechanical transient simulation combined with an improved particle swarm optimization algorithm is designed.Then,the DERs dynamic priority sequence based on the improvement time margin,the state margin,and the preference of the VPP control center and the fast control instruction allocation based on the look-up table is proposed.The case shows that the control cost can be significantly reduced by multiple resources coordination,and the DERs’ dynamic priority can ensure the fairness of different DERs types.