一体化热防护结构通常处于严酷的非稳态热环境,热载荷作用的时间效应(即瞬态热效应)明显.为了避免瞬态热分析的巨大计算消耗,以往的一体化热防护结构优化设计研究通常将瞬态传热等效为相同热边界条件下的稳态传热,将稳态传热分析的温度...一体化热防护结构通常处于严酷的非稳态热环境,热载荷作用的时间效应(即瞬态热效应)明显.为了避免瞬态热分析的巨大计算消耗,以往的一体化热防护结构优化设计研究通常将瞬态传热等效为相同热边界条件下的稳态传热,将稳态传热分析的温度场作为设计热载荷.然而,已有的研究表明稳态传热无法准确等效瞬态传热的作用效果,瞬态热效应对结构设计结果具有重要影响.文章研究了考虑瞬态热效应的一体化热防护结构优化设计问题,建立一种考虑瞬态温度和应力约束的一体化热防护结构拓扑优化方法.该方法以SIMP(solid isotropic material with penalization)法为基础,构建两种针对一体化热防护结构的热弹性结构拓扑优化模型:(1)考虑材料体积分数、最大应力和底面最大温度约束,以最小化结构应变能为目标的刚度设计模型;(2)考虑最大应力和底面最大温度约束,以最小化材料体积分数为目标的轻量化设计模型.通过求解瞬态热力耦合方程获得结构的热力耦合静力分析结果;通过响应量在空间和时间域的凝聚积分函数表征结构响应在时域内的最大值,并以此构建相应的约束和目标函数;采用伴随法推导约束和目标函数的灵敏度表达式.通过3个数值算例验证了本方法的有效性.数值算例结果表明,在瞬态传热条件下,本方法能够准确反映瞬态热效应对一体化热防护结构设计结果的影响;相比于基于稳态热分析的设计结果,考虑瞬态热效应的设计结果具有更优的性能.展开更多
Strong DC coupling with weak AC and large-scale renewable energy integration are the two significant characteristics of ultra-high-voltage AC/DC(UHVAC/DC)hybrid power grids in China.Strong coupling between AC and DC g...Strong DC coupling with weak AC and large-scale renewable energy integration are the two significant characteristics of ultra-high-voltage AC/DC(UHVAC/DC)hybrid power grids in China.Strong coupling between AC and DC grids and the different integration performance of renewable energy sources have profoundly changed the stability characteristics of the power system.The traditional stability control system is inadequate for the stability control of UHVAC/DC power grids.This paper analyzes the requirements for constructing an integrated defense system in a UHVAC/DC hybrid power grid(i.e.power system protection).The definition,connotation,and designing principles of power system protection are put forward.The relationship between the power system protection and the traditional three-defense lines is investigated.The design principles,general hardware structure and main functions of a power system protection are presented.Key problems and technologies are specified in the construction of the power system protection.展开更多
文摘一体化热防护结构通常处于严酷的非稳态热环境,热载荷作用的时间效应(即瞬态热效应)明显.为了避免瞬态热分析的巨大计算消耗,以往的一体化热防护结构优化设计研究通常将瞬态传热等效为相同热边界条件下的稳态传热,将稳态传热分析的温度场作为设计热载荷.然而,已有的研究表明稳态传热无法准确等效瞬态传热的作用效果,瞬态热效应对结构设计结果具有重要影响.文章研究了考虑瞬态热效应的一体化热防护结构优化设计问题,建立一种考虑瞬态温度和应力约束的一体化热防护结构拓扑优化方法.该方法以SIMP(solid isotropic material with penalization)法为基础,构建两种针对一体化热防护结构的热弹性结构拓扑优化模型:(1)考虑材料体积分数、最大应力和底面最大温度约束,以最小化结构应变能为目标的刚度设计模型;(2)考虑最大应力和底面最大温度约束,以最小化材料体积分数为目标的轻量化设计模型.通过求解瞬态热力耦合方程获得结构的热力耦合静力分析结果;通过响应量在空间和时间域的凝聚积分函数表征结构响应在时域内的最大值,并以此构建相应的约束和目标函数;采用伴随法推导约束和目标函数的灵敏度表达式.通过3个数值算例验证了本方法的有效性.数值算例结果表明,在瞬态传热条件下,本方法能够准确反映瞬态热效应对一体化热防护结构设计结果的影响;相比于基于稳态热分析的设计结果,考虑瞬态热效应的设计结果具有更优的性能.
文摘Strong DC coupling with weak AC and large-scale renewable energy integration are the two significant characteristics of ultra-high-voltage AC/DC(UHVAC/DC)hybrid power grids in China.Strong coupling between AC and DC grids and the different integration performance of renewable energy sources have profoundly changed the stability characteristics of the power system.The traditional stability control system is inadequate for the stability control of UHVAC/DC power grids.This paper analyzes the requirements for constructing an integrated defense system in a UHVAC/DC hybrid power grid(i.e.power system protection).The definition,connotation,and designing principles of power system protection are put forward.The relationship between the power system protection and the traditional three-defense lines is investigated.The design principles,general hardware structure and main functions of a power system protection are presented.Key problems and technologies are specified in the construction of the power system protection.