| At present,with the establishment of ‘Carbon Neutrality’ goal of China,renewable energy sources such as wind and photovoltaic power are developing rapidly and extensively.In the context of the uneven geographical distribution of China energy and load,large-scale renewable energy transmitting across provinces via Line Commutated Converter Based HVDC(LCC-HVDC)lines has become an increasingly important transmission mode.For the sending-side grid that contains large-scale wind power delivered via LCC-HVDC,the grid is weak and lacks traditional power support.The grid dispatch center may change the DC transmission commands multiple times during the day due to the fluctuation and uncertainty of wind power,which makes the var and voltage adjustment equipment in converter station near renewable energy stations need frequent adjustment actions accordingly.Therefore,how to fully coordinate the various adjustment methods with different characteristics and action time constants in converter station on various time scales,as well as to carry out voltage safety control and reasonable var distribution has become an important problem for sending-end grid safe operation.This paper is funded by the National Natural Science Foundation of China‘Time-spatial-optimization-coordinated reduced-order equivalent approach of large-scale hybrid AC/DC grid dynamic var reserve assessment’(52007017).This paper regard var and voltage regulation equipment of the LCC-HVDC converter station as the object,researching on the day-ahead global allocation of discrete adjustment resources,the coordinated scheduling method of multiple equipment intraday,and the optimal equipment configuration considering dynamic voltage adjustment requirements.In the day-ahead stage,due to the limited action times of the discrete regulation equipment,in order to solve the problems that the unreasonable allocation of discrete resources may lead to the reduction of dynamic reactive power reserve and voltage safety risks increase in intra-day scheduling,this paper proposed a schedulable time period optimization method based on discrete adjustment equipment action plan under multiple scenarios.he schedulable time period refers to the time period during which discrete adjustment device is allowed to act once mostly intraday.Firstly,this article analyzes and comprehensive modeling the adjustment methods of filter capacitors,inductors,transformer taps,static var compensator(SVC),static var generator(SVG),and DC controller in the converter station with the considering various operating requirements of converter station.The sensitivity-based method is used to linearize the problem of multi-device coupling.Then,a day-ahead discrete adjustment equipment action plan is proposed to calculate the corresponding equipment action plans under different day-ahead wind power forecasting scenarios.Finally,a schedulable time period optimization method is proposed to calculate the schedulable time period of discrete adjustment equipment based on the action plan under different scenarios.The results of the day-ahead resource global allocation can be used to guide intraday dispatch.Case study bases on an improved IEEE-9 system with converter station equipment model.The results show that the proposed method can optimize the action plan of discrete regulating resource in different scenarios,and calculate the intraday schedulable period of the equipment.In the intraday stage,it is necessary to solve the coordinated scheduling problem of multiple regulating devices with different response characteristics,and overcome the conservative or redundant strategy caused by the traditional optimization calculation based on single-time section data.Therefore,this paper proposes a hierarchical scheduling framework from day-ahead to intraday,and proposes a calculation method for intraday equipment coordination scheduling based on model predictive control(MPC)theory.This method takes the day-ahead global allocation of discrete regulation equipment as the action constraint,and supplements the modeling of the converter station operation requirements such as the switching of DC controller and the dynamic reactive power reserve.The method is used to dispatch the DC controller and a variety of discrete/continuous regulating devices based on MPC intraday.The case study analysis verifies the voltage control and var distribution effects of the proposed method,and proves the superiority of intraday rolling optimization based on MPC compared to the traditional optimization method based on single-time section data.The error analysis of the state variables proves the accuracy of the results of the hierarchical scheduling strategy based on the sensitivity linearization power flow method.In order to meet the requirement of bus voltage dynamic regulation in converter station,and to analyze the influence of steady-state continuous reactive power resource investment on equipment allocation,this paper proposes an optimal allocation method for capacity and parameters of continuous var regulation equipment considering dynamic voltage recovery performance.Firstly,the motion process of SVC equipment is modeled based on control theory.Then,the fault scenarios are analyzed and studied,and the typical voltage off-limit scenario extraction method based on amplitude partition is used to reduce the scenario.Finally,a multi-objective optimization model for capacity and response time parameters of continuous reactive power regulating equipment was proposed based on voltage recovery area and expected voltage adjustment value,and the primal-dual path tracking interior point method was used to solve the optimization.The typical fault scenarios causing voltage overlimit were analyzed,and the optimal configuration strategy of the continuous reactive power regulating equipment parameters of the converter station was calculated and compared with the traditional configuration strategy based on experience,and the influence of the steady state input of continuous reactive power on the equipment parameter configuration was further analyzed.The results show that the proposed method can give better consideration to economy and safety in parameter configuration of continuous reactive power regulation equipment in converter station. |
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