Calculation of static voltage stability margin(SVSM)of AC/DC power systems with lots of renewable energy sources(RESs)integration requires consideration of uncertain load growth and renewable energy generation output....Calculation of static voltage stability margin(SVSM)of AC/DC power systems with lots of renewable energy sources(RESs)integration requires consideration of uncertain load growth and renewable energy generation output.This paper presents a bi-level optimal power flow(BLOPF)model to identify the worst-case SVSM of an AC/DC power system with line commutation converter-based HVDC and multi-terminal voltage sourced converter-based HVDC transmission lines.Constraints of uncertain load growth’s hypercone model and control mode switching of DC converter stations are considered in the BLOPF model.Moreover,uncertain RES output fluctuations are described as intervals,and two three-level optimal power flow(TLOPF)models are established to identify interval bounds of the system worst-case SVSM.The two TLOPF models are both transformed into max–min bi-level optimization models according to independent characteristics of different uncertain variables.Then,transforming the inner level model into its dual form,max–min BLOPF models are simplified to single-level optimization models for direct solution.Calculation results on the modified IEEE-39 bus AC/DC case and an actual large-scale AC/DC case in China indicate correctness and efficiency of the proposed identification method.展开更多
With the rapid load increase in some countries such as China, power grids are becoming more strongly interconnected, and the differences between peak and valley loads are also increasing. As a result, some bulk power ...With the rapid load increase in some countries such as China, power grids are becoming more strongly interconnected, and the differences between peak and valley loads are also increasing. As a result, some bulk power systems are facing high voltage limit violations during light-load periods. This paper proposes to utilize transmission switching(TS) to eliminate voltage violations. The TS problem is formed as a mixed-integer nonlinear program(MINLP) with AC power flow constraints and binary variables. The proposed MINLP problem is non-deterministic polynomial hard.To efficiently solve the problem, a decomposition approach is developed. This approach decomposes the original problem into a mixedinteger linear programming master problem and an AC optimal power flow slave problem that is used to check the AC feasibility. Prevention of islanding is also taken into consideration to ensure the feasibility of the TS results.The modified IEEE 39-bus and IEEE 57-bus test systems are used to demonstrate the applicability and effectiveness of the proposed method.展开更多
This paper proposes a stochastic programming(SP)method for coordinated operation of distributed energy resources(DERs)in the unbalanced active distribution network(ADN)with diverse correlated uncertainties.First,the t...This paper proposes a stochastic programming(SP)method for coordinated operation of distributed energy resources(DERs)in the unbalanced active distribution network(ADN)with diverse correlated uncertainties.First,the threephase branch flow is modeled to characterize the unbalanced nature of the ADN,schedule DER for three phases,and derive a realistic DER allocation.Then,both active and reactive power resources are co-optimized for voltage regulation and power loss reduction.Second,the battery degradation is considered to model the aging cost for each charging or discharging event,leading to a more realistic cost estimation.Further,copulabased uncertainty modeling is applied to capture the correlations between renewable generation and power loads,and the twostage SP method is then used to get final solutions.Finally,numerical case studies are conducted on an IEEE 34-bus three-phase ADN,verifying that the proposed method can effectively reduce the system cost and co-optimize the active and reactive power.展开更多
Phasor measurement units(PMUs)are preferred for installation at weak buses in a power network.Therefore,the weak buses need to be located and the strategic locations of PMUs identified to ensure network observability....Phasor measurement units(PMUs)are preferred for installation at weak buses in a power network.Therefore,the weak buses need to be located and the strategic locations of PMUs identified to ensure network observability.Thus,the primary aim of this work is to identify the placements of the maximum number of PMUs installed at the weak buses in the electrical network.The voltage collapse proximity indicator,line stability index,fast voltage stability index,and a new voltage stability indicator utilizing load flow measurement are used to determine the weak buses.A novel deterministic methodology based on a binary-integer linear programming model is then proposed to determine the optimal locations of PMUs.The effect of a single PMU outage considering the weak buses is also demonstrated.The effectiveness of the developed approach is tested and validated on the standard IEEE 14-,118-,300-,and New England 39-bus systems.The obtained results are also compared to those using different weak bus methodologies.展开更多
In addition to increasing penetration of distributed generation(DG),the distribution system power flow may be significantly impacted by direction and magnitude.This paper proposes a method for optimal placement of win...In addition to increasing penetration of distributed generation(DG),the distribution system power flow may be significantly impacted by direction and magnitude.This paper proposes a method for optimal placement of wind DG considering the unbalanced operation of distribution systems.The objective function includes static voltage stability index,three-phase unbalance index,system reliability index,and DG investment cost.The untransposed distribution lines and unbalanced load are modelled,and corresponding static voltage stability index and system reliability considering DG penetrations are derived.The expected and stochastic daily distributed generation and demand profiles in four seasons are calculated to improve the accuracy.To solve this multi-objective optimization model,a fuzzy membership function is used to integrate the four individual objectives,and a sensitivity-based method is proposed to solve the model efficiently.Case study on IEEE 13-bus distribution 3-phase networks and 123-node test feeder successfully verifies the performance of the proposed approach.展开更多
Various optimizations in power systems based on the AC power flow model are inherently mixed-integer nonlinear programming(MINLP)problems.Piecewise linear power flow models can handle nonlinearities and meanwhile ensu...Various optimizations in power systems based on the AC power flow model are inherently mixed-integer nonlinear programming(MINLP)problems.Piecewise linear power flow models can handle nonlinearities and meanwhile ensure a hi^h accuracy.Then,the MINLP problem can he turned into a tractable mixed-integer linear programming(MILP)problem.However,piecewise linearization also introduces a heavy computational burden because of the incorporation of a large number of binary variables especially for large systems.To achieve a better trade off between approximation accuracy and computational efficiency,this paper proposes a model called decoupled piecewise linear power flow(DPWLPF)for transmission systems.The P-Q decoupling characteristic is used to ease the evaluation of the piecewise cosine functions in the power flow equations.Therefore,in optimizations,the coupling between variables is reduced.Moreover,an under voltage load shedding(UVLS)approach based on DPWLPF is presented.Case studies are conducted for benchmark systems.The results show that the DPWLPF facilitates the solution of optimal power flow(OPF)and UVLS problems much better than conventional piecewise models.And DPWIJM^still enhances the approximation accuracy by usinj»the decoupled piecewise modeling.展开更多
Step channel direct injection(SCDI)flash memory device which had been developed changes the hot carrier injection method by making a shallow step in the middle of channel .Therefore high speed for programming,hig...Step channel direct injection(SCDI)flash memory device which had been developed changes the hot carrier injection method by making a shallow step in the middle of channel .Therefore high speed for programming,high efficiency for injection,and lower working voltage are obtained.Simulation and analysis for the proposed SCDI structure device are done and an optimization scheme to improve the utmost performance of SCDI device is given...展开更多
为解决传统比例?积分?微分(proportional integral differential,PID)控制应用于静止无功补偿器(static var compensator,SVC)非线性控制系统存在的不足,提出了一种基于自适应动态规划(adaptive dynamic programming,ADP)的SVC自适应优...为解决传统比例?积分?微分(proportional integral differential,PID)控制应用于静止无功补偿器(static var compensator,SVC)非线性控制系统存在的不足,提出了一种基于自适应动态规划(adaptive dynamic programming,ADP)的SVC自适应优化控制策略。采用小波神经网络和BP神经网络分别设计执行依赖启发式动态规划(action dependent heuristic dynamic programming,ADHDP)的执行网络和评价网络,以增强ADHDP对性能指标函数的逼近能力和控制律优化能力,然后用其设计了SVC控制系统的电压调节器。在Matlab/Simulink仿真平台对所提出的ADHDP控制方法进行了仿真,并与执行网络、评价网络均采用BP神经网络设计的经典ADHDP控制方法的控制效果进行了对比,验证了基于ADHDP的SVC电压优化控制方法的可行性和有效性。相比之下,所提出的ADHDP控制方法具有更好的电压稳定和控制效果,控制系统具有较快的响应速度、较好的动态和静态稳定性和较强的自适应能力。展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51977080)the Natural Science Foundation of Guangdong Province(Grant No.2022A1515010332)supported by the U.S.National Science Foundation(Grant#2124849).
文摘Calculation of static voltage stability margin(SVSM)of AC/DC power systems with lots of renewable energy sources(RESs)integration requires consideration of uncertain load growth and renewable energy generation output.This paper presents a bi-level optimal power flow(BLOPF)model to identify the worst-case SVSM of an AC/DC power system with line commutation converter-based HVDC and multi-terminal voltage sourced converter-based HVDC transmission lines.Constraints of uncertain load growth’s hypercone model and control mode switching of DC converter stations are considered in the BLOPF model.Moreover,uncertain RES output fluctuations are described as intervals,and two three-level optimal power flow(TLOPF)models are established to identify interval bounds of the system worst-case SVSM.The two TLOPF models are both transformed into max–min bi-level optimization models according to independent characteristics of different uncertain variables.Then,transforming the inner level model into its dual form,max–min BLOPF models are simplified to single-level optimization models for direct solution.Calculation results on the modified IEEE-39 bus AC/DC case and an actual large-scale AC/DC case in China indicate correctness and efficiency of the proposed identification method.
文摘With the rapid load increase in some countries such as China, power grids are becoming more strongly interconnected, and the differences between peak and valley loads are also increasing. As a result, some bulk power systems are facing high voltage limit violations during light-load periods. This paper proposes to utilize transmission switching(TS) to eliminate voltage violations. The TS problem is formed as a mixed-integer nonlinear program(MINLP) with AC power flow constraints and binary variables. The proposed MINLP problem is non-deterministic polynomial hard.To efficiently solve the problem, a decomposition approach is developed. This approach decomposes the original problem into a mixedinteger linear programming master problem and an AC optimal power flow slave problem that is used to check the AC feasibility. Prevention of islanding is also taken into consideration to ensure the feasibility of the TS results.The modified IEEE 39-bus and IEEE 57-bus test systems are used to demonstrate the applicability and effectiveness of the proposed method.
文摘This paper proposes a stochastic programming(SP)method for coordinated operation of distributed energy resources(DERs)in the unbalanced active distribution network(ADN)with diverse correlated uncertainties.First,the threephase branch flow is modeled to characterize the unbalanced nature of the ADN,schedule DER for three phases,and derive a realistic DER allocation.Then,both active and reactive power resources are co-optimized for voltage regulation and power loss reduction.Second,the battery degradation is considered to model the aging cost for each charging or discharging event,leading to a more realistic cost estimation.Further,copulabased uncertainty modeling is applied to capture the correlations between renewable generation and power loads,and the twostage SP method is then used to get final solutions.Finally,numerical case studies are conducted on an IEEE 34-bus three-phase ADN,verifying that the proposed method can effectively reduce the system cost and co-optimize the active and reactive power.
文摘Phasor measurement units(PMUs)are preferred for installation at weak buses in a power network.Therefore,the weak buses need to be located and the strategic locations of PMUs identified to ensure network observability.Thus,the primary aim of this work is to identify the placements of the maximum number of PMUs installed at the weak buses in the electrical network.The voltage collapse proximity indicator,line stability index,fast voltage stability index,and a new voltage stability indicator utilizing load flow measurement are used to determine the weak buses.A novel deterministic methodology based on a binary-integer linear programming model is then proposed to determine the optimal locations of PMUs.The effect of a single PMU outage considering the weak buses is also demonstrated.The effectiveness of the developed approach is tested and validated on the standard IEEE 14-,118-,300-,and New England 39-bus systems.The obtained results are also compared to those using different weak bus methodologies.
基金supported in part by the 2015 Science and Technology Project of China Southern Power Grid(WYKJ00000027)in part by funding from mid-career researcher development scheme,the Faculty of Engineering&Information Technologies,The University of Sydney.
文摘In addition to increasing penetration of distributed generation(DG),the distribution system power flow may be significantly impacted by direction and magnitude.This paper proposes a method for optimal placement of wind DG considering the unbalanced operation of distribution systems.The objective function includes static voltage stability index,three-phase unbalance index,system reliability index,and DG investment cost.The untransposed distribution lines and unbalanced load are modelled,and corresponding static voltage stability index and system reliability considering DG penetrations are derived.The expected and stochastic daily distributed generation and demand profiles in four seasons are calculated to improve the accuracy.To solve this multi-objective optimization model,a fuzzy membership function is used to integrate the four individual objectives,and a sensitivity-based method is proposed to solve the model efficiently.Case study on IEEE 13-bus distribution 3-phase networks and 123-node test feeder successfully verifies the performance of the proposed approach.
基金supported by China Postdoctoral Science Foundation(2020M670325).
文摘Various optimizations in power systems based on the AC power flow model are inherently mixed-integer nonlinear programming(MINLP)problems.Piecewise linear power flow models can handle nonlinearities and meanwhile ensure a hi^h accuracy.Then,the MINLP problem can he turned into a tractable mixed-integer linear programming(MILP)problem.However,piecewise linearization also introduces a heavy computational burden because of the incorporation of a large number of binary variables especially for large systems.To achieve a better trade off between approximation accuracy and computational efficiency,this paper proposes a model called decoupled piecewise linear power flow(DPWLPF)for transmission systems.The P-Q decoupling characteristic is used to ease the evaluation of the piecewise cosine functions in the power flow equations.Therefore,in optimizations,the coupling between variables is reduced.Moreover,an under voltage load shedding(UVLS)approach based on DPWLPF is presented.Case studies are conducted for benchmark systems.The results show that the DPWLPF facilitates the solution of optimal power flow(OPF)and UVLS problems much better than conventional piecewise models.And DPWIJM^still enhances the approximation accuracy by usinj»the decoupled piecewise modeling.
文摘Step channel direct injection(SCDI)flash memory device which had been developed changes the hot carrier injection method by making a shallow step in the middle of channel .Therefore high speed for programming,high efficiency for injection,and lower working voltage are obtained.Simulation and analysis for the proposed SCDI structure device are done and an optimization scheme to improve the utmost performance of SCDI device is given...
