Rapid development of renewable energy in China is driving a major shift in the characteristics and control requirements of the electricity grid.Since the best renewable energy resources are far away from load centers ...Rapid development of renewable energy in China is driving a major shift in the characteristics and control requirements of the electricity grid.Since the best renewable energy resources are far away from load centers in the east and southeast,transmission over long distances is required.Over 20 high-voltage DC(HVDC)transmission lines,with a combined capacity exceeding 150 GW,are in operation or are currently under construction.This rapid expansion of new generation and transmission capacities based on power electronics starts to change the characteristics of the grid,especially in areas where they concentrate,creating new stability problems and operational challenges.New system theories and technologies are required to support the development and operation of a future grid that relies more and more on power electronics.This paper highlights the characteristics of power electronics as used in renewable energy generation and HVDC transmission systems,discusses the impacts of these power-electronics-based assets on grid stability and operational requirements,and identifies opportunities for the development of both new system theories and system technologies to support a national energy policy that emphasizes the use of clean energy.展开更多
风电场电压受风力影响容易快速波动,传统基于当前时间断面进行决策的方法易出现无功控制滞后、多种设备不协调等问题。为此,基于模型预测控制(model predictive control,MPC)理论,提出了一种旨在协调风力机和静止无功发生器(static var ...风电场电压受风力影响容易快速波动,传统基于当前时间断面进行决策的方法易出现无功控制滞后、多种设备不协调等问题。为此,基于模型预测控制(model predictive control,MPC)理论,提出了一种旨在协调风力机和静止无功发生器(static var generator,SVG)的风电场电压控制方法。区别于传统电压控制方法,所提出方法的目标是实现未来时间窗内电压控制曲线和无功调节动态过程的优化。利用自回归滑动平均方法预测风力机的有功出力,并分别以一阶惯性环节和比例积分环节模拟风力机和SVG无功控制的动态过程,在此基础上利用灵敏度预测求解风电场内各母线(含风力机机端母线)的未来电压曲线。由此建立了以目标函数为未来时间窗内并网点电压偏移最小和SVG动态无功储备最大的优化模型,并采用对偶单纯形法求解。在基于DIgSILENT建立的风电场仿真系统上进行了仿真验证。时域仿真结果表明,所提出的方法通过预测不同设备未来一段时间的控制动态过程,能合理安排快、慢无功出力,提前响应系统中可预见变化,保证风力机机端电压安全,并维持并网点电压平稳。展开更多
建立了基于非结构三角网格系统的非恒定浅水二维水流数学模型。基本控制方程采用浅水二维水流方程;采用能够有效捕捉激波的HLLC近似黎曼算子求解界面通量,并对界面变量进行数据重构,模型具有二阶精度;将地形高程定义在三角单元节点上,...建立了基于非结构三角网格系统的非恒定浅水二维水流数学模型。基本控制方程采用浅水二维水流方程;采用能够有效捕捉激波的HLLC近似黎曼算子求解界面通量,并对界面变量进行数据重构,模型具有二阶精度;将地形高程定义在三角单元节点上,使得单元间地形连续变化,结合处理底坡的DFB(divergence form for bed slope source term)方法,保证了模型的和谐性,使其能够有效地模拟不规则地形条件上干湿边界变化过程中的水流过程;采用了隐式方法处理阻力项,从而保证了模型的稳定性。最后,通过四个经典算例对模型进行了系统地检验。结果表明:此模型具有很好的和谐性和稳定性,能够有效、准确地模拟复杂地形情况下水流运动,显示了广阔的应用前景。展开更多
基金supported in part by the State Grid Science and Technology Project“Impedance-Based Modeling and Control of Distributed Generation Systems”(NYB1720170218).
文摘Rapid development of renewable energy in China is driving a major shift in the characteristics and control requirements of the electricity grid.Since the best renewable energy resources are far away from load centers in the east and southeast,transmission over long distances is required.Over 20 high-voltage DC(HVDC)transmission lines,with a combined capacity exceeding 150 GW,are in operation or are currently under construction.This rapid expansion of new generation and transmission capacities based on power electronics starts to change the characteristics of the grid,especially in areas where they concentrate,creating new stability problems and operational challenges.New system theories and technologies are required to support the development and operation of a future grid that relies more and more on power electronics.This paper highlights the characteristics of power electronics as used in renewable energy generation and HVDC transmission systems,discusses the impacts of these power-electronics-based assets on grid stability and operational requirements,and identifies opportunities for the development of both new system theories and system technologies to support a national energy policy that emphasizes the use of clean energy.
文摘风电场电压受风力影响容易快速波动,传统基于当前时间断面进行决策的方法易出现无功控制滞后、多种设备不协调等问题。为此,基于模型预测控制(model predictive control,MPC)理论,提出了一种旨在协调风力机和静止无功发生器(static var generator,SVG)的风电场电压控制方法。区别于传统电压控制方法,所提出方法的目标是实现未来时间窗内电压控制曲线和无功调节动态过程的优化。利用自回归滑动平均方法预测风力机的有功出力,并分别以一阶惯性环节和比例积分环节模拟风力机和SVG无功控制的动态过程,在此基础上利用灵敏度预测求解风电场内各母线(含风力机机端母线)的未来电压曲线。由此建立了以目标函数为未来时间窗内并网点电压偏移最小和SVG动态无功储备最大的优化模型,并采用对偶单纯形法求解。在基于DIgSILENT建立的风电场仿真系统上进行了仿真验证。时域仿真结果表明,所提出的方法通过预测不同设备未来一段时间的控制动态过程,能合理安排快、慢无功出力,提前响应系统中可预见变化,保证风力机机端电压安全,并维持并网点电压平稳。
文摘建立了基于非结构三角网格系统的非恒定浅水二维水流数学模型。基本控制方程采用浅水二维水流方程;采用能够有效捕捉激波的HLLC近似黎曼算子求解界面通量,并对界面变量进行数据重构,模型具有二阶精度;将地形高程定义在三角单元节点上,使得单元间地形连续变化,结合处理底坡的DFB(divergence form for bed slope source term)方法,保证了模型的和谐性,使其能够有效地模拟不规则地形条件上干湿边界变化过程中的水流过程;采用了隐式方法处理阻力项,从而保证了模型的稳定性。最后,通过四个经典算例对模型进行了系统地检验。结果表明:此模型具有很好的和谐性和稳定性,能够有效、准确地模拟复杂地形情况下水流运动,显示了广阔的应用前景。
